Chapter 7 Container Seedlings John C. Brissette, James P. Barnett, and Thomas D. Landis
Other valuable references for the production and use of container southern pine seedlings are publications by Guldin and Barnett [42], Guldin [41], and Barnett and Brissette [19].
7.2 Merits of Container Planting
The many advantages of container seedlings over bareroot stock have been discussed [43, 59, 101, 103, 107]. Container southern pines can be produced quickly (Table 7.1). Plantable loblolly pine (Pinus taeda L.) and slash pine (P. elliottii Engelm. var. elliottii) can be grown in 12 to 14 weeks, longleaf (P. palustris Mill.) in about 16 weeks. Such rapid production allows seedlings to be fall-planted in Abstract years when early survival checks indicate replanting will be necessary. Seedlings grown for progeny tests can be Container southern pine seedlings offer an alternative produced and outplanted the spring after seed collection. In to bareroot stock, especially when short production both cases a year is saved relative to bareroot methods. times are required, the planting season is to be ex- Production flexibility allows container seedlings to be tended, or adverse sites are to be planted. Acceptable planted throughout an extended planting season, provided container seedlings can be produced under various that soil moisture and climatic conditions are favorable for degrees of environmental control and in several growth. Container seedlings tend to perform better on container types. However, seedling quality depends on adverse sites than bareroot seedlings; in some cases, use of the quality of the seeds sown and proper use and timing container stock may be the only way to successfully of cultural practices, especially sowing techniques, reclaim severely damaged sites such as mine spoils or to growing-medium moisture, and seedling nutrition. establish seedlings under droughty conditions as in Shoot and root morphology can be controlled when seed- shelterbelts. Because growing conditions can be better lings are grown in containers to produce stock of controlled, container planting offers potentially increased desired characteristics for outplanting under specified seed efficiency, i.e., the ratio of plantable seedlings to filled conditions. Handling and planting methods used with seeds. This is especially important for valuable or limited container southern pines depend on the time of year and physiological condition of the seedlings. bl 7 1 Adv nt nd d dv nt f nt n r- r n th rn p n dl n
7.1 Introduction
Pine forests in the South are usually established by planting bareroot seedlings, although natural regeneration and direct seeding are used to a limited extent (see chapter 3, this volume). However, planting container seedlings offers land managers a regeneration technique proven beneficial for establishing hard-to-regenerate pine species, regenerating difficult sites, and extending the planting season. An overview of the merits and methods of producing container pine seedlings in the southern United States is presented in this chapter, emphasizing how such methods impact seedling survival and growth after outplanting. seed sources, such as clonal seed-orchard lots (see chapter paperpot containers survive better but have a growth lag, 11). compared to larger bareroot stock [54, 69, 99]. However, some disadvantages exist in production and There have been few good comparative trials with the use of container seedlings [10, 102]. The conditions that southern pines because it is difficult to obtain stock of hasten container seedling development are also conducive similar morphology and physiology. However, survival of to disease, nutritional imbalances, and other problems. container seedlings has generally exceeded that of bareroot Trees produced in containers will likely cost more than nursery stock, and growth comparisons have been good [8, bareroot stock from existing, depreciated nurseries, but not 1 38, 100]. Container stock clearly outperforms bareroot necessarily more than seedlings from a new bareroot seedlings when age from seed is considered [38]. nursery [41]. Container seedlings are bulkier to transport When outplanted at the same time, container seedlings and must be handled differently from bareroot seedlings can perform as well as or better than bareroot seedlings (see 7.11). On sites with severe herbaceous competition, when high-quality stock is used. Goodwin [39] found that more complete site preparation may be necessary for after five growing seasons, container longleaf pine seed- success with container seedlings, which have smaller initial lings survived better and grew faster than 1+0 bareroot seed- size [96]. lings when planted on sandhill sites. He concluded that Although biological and production advantages can be container longleaf seedlings could be used to extend the realized from growing seedlings in containers, their normal planting season and to replant 1+0 seedling failures acceptance by foresters depends upon field performance. in the same growing season if soil moisture was sufficient. Survival of western conifer seedlings grown in containers Amidon et al. [1] reported that, under droughty condi- has usually equaled or exceeded that of bareroot nursery tions, container longleaf pine seedlings survived and grew stock [4, 36, 45, 103, 107, 116]. In eastern Canada, results better than bareroot stock when the container seedlings with northern conifers indicate that seedlings grown in were outplanted in late summer before the normal bareroot planting season. Even under severe moisture stress, container seedlings performed better than bareroot seed- lings when outplanted at the same time in early spring. In a direct comparison between container and bareroot loblolly pine seedlings planted in March and May, South and Barnett [100] found no difference when soil moisture was adequate at the time of planting. However, when both stock types were in relatively dry soil, the container seedlings survived better.
7 3 l nd l t f r S dl n r d t n
7 3 1 S t S l t n Sites for container nursery facilities require much less stringent criteria than sites for new bareroot nurseries. Topography and soil constraints that may prohibit the development of a bareroot nursery would not deter construction of a container facility. Important consider- ations for selecting a container nursery site include management objectives, location of outplanting sites, climate, water supply and quality, road access and utilities, labor supply, and proximity to mills and other manufactur- ing facilities. Hahn [44] provides some valuable insights into these and other aspects of site selection; Barnett and Brissette [19] discuss aspects that are unique to the South.
7 3 Str t r Structures for growing container seedlings in the South r 7 1 ( S pl h d h t bl f r pr d n may vary from benches in the open to simple shadehouses nt n r th rn p n d r n h f th r nd f r d- to elaborate glass greenhouses (Fig. 7.1). Generally, seed- l n h rd n n d r n f ll nd nt r (b M r l b r t l r nh th nv r n nt l ntr l t bl f r lings can be grown in the open without a structure or, at pr d n nt n r dl n thr h t th r ( d pt d most, in semicontrolled greenhouses in the Coastal Plain fr G ld n [ 1] areas of the South. In fact, recent research has shown that these products have been evaluated in the South [7]. In addition, kraft-paper tubes, polyurethane foam blocks, biodegradable plastic tubes, and peat-vermiculite blocks have been developed primarily for southern use [6, 21].
7.4.1 Types of Containers Because the type of container has both major and direct impacts on seedling quality and production costs, silvicul- turists as well as nursery managers must be familiar with the various container types available. The many container products can be divided into three general types: tubes, plugs, and blocks (Fig. 7.2). Each type has certain merits that should be considered in relation to the intended outplanting sites before a container system is selected.
7 1 1 b Tubes are containers that have an exterior wall, require filling with a growing medium, and are planted with the seedlings. Their primary advantage is wall rigidity. This provides both ease of handling and sufficient imper- meability to prevent seedlings from desiccating when planted in dry soil [31]. Their major disadvantage is the slow egress of roots into soil because initial contact with the soil is made primarily through the bottom of the tube. On the basis of performance evaluations with the southern pines and commercial availability, the Paperpot is probably r 7 bl ll p n dl n r n n thr nt n r the best tube-type container [16]. The Japanese Paperpot t p ( b d r d bl pl t t b (b p t -v r- does not degrade rapidly. The Finnish Paperpot® is l t ld d bl nd ( pl fr St r bl - reportedly manufactured of material that allows faster root egress, but this can lead to root growth between containers the quality of longleaf and loblolly pines grown outside during the growing phase and subsequent root damage with no shade is superior to that of seedlings grown in during extraction. Therefore, only small trees or short greenhouses [18] (see 7.7.2). However, if crops are to be rotations are recommended if Paperpots are used. Root produced over winter, an enclosed, adequately heated spiraling also is a problem [21]. structure is required. The type of structure, or lack of it, depends on manage- 7 1 l ment objectives that must take into account biological, Plugs are molded blocks containing cavities filled with l t n nd p r t n l f t r G ld n [41] growing medium. They are the preferred container for compared the economics of various combinations of operational use in the Pacific Northwest and Canada and facility, container type, and climatic zone for container and are easily planted by hand or machine. But, unlike with bareroot seedling production; McDonald [70] discusses the tubes or blocks (see 7.4.1.3), the rooted seedlings are relative merits of greenhouses with fully controlled and removed from their plug containers before outplanting and semicontrolled environments. are planted along with the growing medium. Because roots are not constrained after planting, they rapidly establish 7.4 Containers themselves in the surrounding soil. However, seedlings must be held in plug containers long enough for roots to The great impetus for container planting in North bind the soil and facilitate extraction. The holding time America resulted from Walters' publication [119] of his varies with the size of the container cavity and species of technique using the plastic bullet and planting gun. Jones tree; generally, the minimum is 3 to 5 months. Ray Leach [51] reported early evaluations of seedlings grown in kraft- Single Cells, Rootrainers, and Styroblocks can produce paper containers in the South. Since those beginnings, a excellent plug seedlings. host of container types have emerged for forestry use, Ray Leach Single Cells can be handled individually for primarily for nothern and western situations. Included are randomization, removal of blanks, and transport. products such as plastic bullets, Ontario tubes, BC/CFS Rootrainers open to allow inspection of the root system and Styroblocks®, Rootrainers®, extruded peat cylinders, easy removal of the plug. The BC/CFS Styroblock was Japanese Paperpots®, Ray Leach Single Cells®, plastic- developed in Canada to overcome root-configuration mesh tubes, and wood-fiber blocks [110, 117]. Most of problems inherent with plastic bullets. Growth of slash pine dl n ft r tpl nt n fr v r l nt n r t p h d th t th fr th St r bl - ( - n 3 v l l d r x d d ll th r x pt th bl -t p K t St ® h dd l nt r l t® h r v t th n bt t p r f r dl n xtr t n v r th th t l r n b r f dl n r pr d d p r n t r th n th t th r nt n r t
7 1 3 l l d n n rp r t dv nt f t b nd pl h bl t lf b th th nt n r nd th r n d ; d r n n th bl nd th nt r p tr n pl nt d nt th l l r ll r d n h f r h n z d pl nt n b t t ll ll r p d r t r p n tpl nt n Of th t bl -t p nt n r v l t d th th rn p n th K t St r p r r t th Gr -bl ® nd r b t n v r l nt n r t p t t d Unf rt n t l th r 7 3 Eff t f t nt n r p r t r n d v l p- pr d t n l n r r ll v l bl nt nd f ld p rf r n f l bl ll p n dl n r ht r r d t t f tpl nt n h ht nd 7 C nt n r S z rv v l ft r 3 r n th f ld M t nt n r n p r t n l h v v l f t 1 5 3 ( 5 t 1 n 3 A 1 - t 1 - ( - t 5- n l n th n r ll t f t r f r th th rn p n nd 7 3 C nt n r nd t v l p nt d t r f 5 t 3 (1 t 1 5 n n l O r r lt th th rn p n nd t th t th n- [7] v r rn tt nd r tt [19] h v h n th t tr nt f n nt n r dv r l ff t dl n nt n r v l l r t l th n dl n d n t n th r th h pr bl r pr r l th t b -t p nt n r (n b r p r n t r ( 7 3 r x pl nt n r th t r pl nt d th th dl n b t n l lth h dd l nt r l t h d 5 l v l d- r n dl n th t r xtr t d fr nt n r b f r l n t t f tpl nt n r b t t h v n tpl nt n r x pl pl t b ll t n l t r t th dd l nt r n th p n p rp t h r n th f ld t th xt nt th t r th t nt d ( d ff r n r lt d pr r l fr th h ll r 7 5 Oth r nt n r t p n r t tr n l t n n b r f dl n r n p r n t r — 31 v ( 7 5b r r t p r l n ( 7 5 If h v r th 1 57/ ( 9 v 15 /ft f r dd l nt r nd p rp t bv xtr f d f r t r v d d th h l r r dl n l p rf r d b tt r n th f ld In nf r t n p d b th nt n r n t dv r l f t dl n d v l p nt v n n th ll dd l nt r ff t f ld p rf r n [ 5 3 (1 5 n 3 ] b th n th r nh nd f ld St d h v l h n th t th d r f r t lf r- b tt r th n n th p rp t [ 3 (5 3 n 3 ] h ff t t n n th f ld v r th p nd l t p f d n t d r n th r n p r d b v n l r r n l f p n r pt bl t r t p r l n th n h n nt n r v l r n n t nt l bl ll r l h pr b bl b t rl r t l n t n h p r d f r h h dl n r r n b f r tpl nt n l nt r t th d n t ( 7 If r n p r d r l t d t t 1 p n h l ff t n d v l p nt b dl n r ll r n t x d n b t 1 75/ (1 /ft r d n t l d v l p- nt nd r lt n f ld p rf r n f th th rn p n Alth h l r n f d n t nt n t pr v d v l p nt nd p rf r n f t r h th t f pr d t n p ll l nfl n th r l t n h p f nt n r z nd d n t h p n l nfl n th r l t n h p f nt n r z nd d n t t p rf r n r x pl l n l f p n h h v r nt l r nt f h d n d v l p f r b tt r h n r n n l r r v l nt n r t l r d n t ( bl 7 St d t r f l n l f p n r 7 Eff t f t nt n r p r t r n d v l p- nt nd f ld p rf r n f l bl ll p n dl n n r d h n r n n St r bl - n t d f S dl n h r t r t r r d t t f tpl nt n
St r bl - nt n r p r d t nl 19 f r l bl ll h ht nd rv v l ft r - 1/ r n th f ld p n 1 bl 7 v l p nt f l bl ll nd l n l f p n dl n r l t d t nt n r z nd dl n d n t
is more rapid. Heavy clay soils can also increase root malformation, especially root spiraling, by limiting rapid root egress through the punched planting-hole wall [10]. However, if reasonable precautions are taken in selecting containers and planting techniques, root configuration should not adversely affect seedling growth and develop- ment. Adverse root forms increase rapidly with the length of time seedlings are grown in containers. But if growing cycles are kept to 12 to 15 weeks, there should be no problem with properly designed containers.
r 7 5 bl ll p n dl n ( x v t d 3 r ft r tpl nt n n pl t b ll t th t nt d r t ; (b x v t d 3 r ft r tpl nt n n C n d® h-t p nt n r th tr n l t d r t ; nd ( x v t d ft r tpl nt n t r pl th p r l n r t 7.4.4 Containers for Specific Applications T bl . . rv v l nd r th f l n l f p n dl n n t dr t f ll n xtr l h r h dr ht nd t n n r 80 ( d pt d fr d n t l. ] r nt 7.4.4.1 Hand planting t n n J n r 8 . Seedlings grown in plug-type containers are generally most suitable to hand planting. The planting rate of container seedlings with punch-type dibbles usually exceeds that of bareroot stock because of the tapered configuration of the root mass [114]. The planting hole does not have to be closed with the dibble as for bareroot seedlings if the punch is shaped like the container plug. Several planting tools for plugs are also designed so that the seedlings are dropped through the barrel of the tool and the planter does not have to bend over. Both tubes and blocks, being blunted at their ends, are more difficult to hand plant than plugs. Exceptions are tube containers shaped like bullets, but these still seriously constrict the root system and inhibit growth [3].
7.4.4.2 Machine planting Although extractable plugs seem well suited to hand planting, they are not well adapted to automated planting [34]. Tube- and block-type containers lend themselves more easily to a mechanized planting system because of their rigidity and durability. Edwards [35] discusses the development of semiautomatic and automatic planters and related problems.
Certain site and soil types are difficult to plant with 7.4.4.3 Forest genetics programs success: (1) dry, sandy soils, (2) mine spoil banks, (3) Growing seedlings in containers allows efficient use of highly erodible soils, and (4) poorly drained soils. Many of limited quantities of seeds and provides very uniform seed- the dry, sandy soils throughout the South were originally lings. With containerization, progeny tests could begin a longleaf pine sites, but difficulties in planting have slowed year before they would be possible with bareroot tech- regeneration of these areas. Amidon et al. [1] showed that niques because container seedlings can be grown during container longleaf seedlings did much better than bareroot winter if seeds have been properly extracted and can be seedlings on these harsh sites (Table 7.3). Mine spoils outplanted one growing season earlier than bareroot seed- represent a relatively small total acreage, but they are very lings [113]. difficult sites to regenerate in parts of the South. Davidson It may be desirable to sow seeds for progeny tests in and Sowa [30] demonstrated that container seedlings may containers larger than normally used operationally so that do well on these areas, particularly when seedlings are high-quality seedlings develop in a relatively short time. inoculated with mycorrhizae adapted to these soils [63]. Ray Leach Single Cells are ideal because placement of Dickerson [32] also reported that container seedlings gave individual trees can be randomized in the greenhouse, promising results on forest sites severely eroded by poor blank cavities can be removed, and seedlings per unit area agricultural practices. Early-summer planting of container and other factors affecting seedling quality can be easily seedlings is a practical means of regenerating many of the controlled. low-lying poorly drained soils too wet to plant in winter.
1.4.4.4 Problem species and sites Longleaf pine is often difficult to grow in bareroot 7.5 Growing Medium nurseries. Because of its dormant epicotyl or "grass stage" growing characteristic, roots of longleaf develop early; A number of workers have evaluated combinations of when bareroot longleaf seedlings are lifted, a large soil mixes for containers [33, 38, 46, 68, 83, 90]. Almost proportion of their root system is lost, and the resulting without exception, the best combination included sphag- field survival is usually lower than for other southern pine num peat moss and vermiculite. Sphagnum moss provides species. However, when longleaf are grown in containers, good water-holding and buffering capacities, low pH, and their root systems remain intact when planted. high cation-exchange capacity. Vermiculite provides pore space, thus ensuring well-aerated roots. The ratio of peat to T bl .4. r th f 2 ld h rtl f p n dl n n vermiculite most often used is 1:1 but may be 2:1. thr t p f d ( d pt d fr P 8 ] . Domestic peat moss is generally unsatisfactory because the quantities of nutrients, especially nitrogen, are variable, and because it is usually too decomposed to provide the necessary structure and water drainage [90]. Canadian peat moss is recommended, but because of the transportation costs to the South, alternative materials have been evaluated. Because pine bark is readily available and relatively inexpensive, it has been suggested as an alternative to peat moss in growing media [98]. Results to date have indicated that bark does have physical properties that make it a possible alternative to peat moss [27, 91], allows excellent mycorrhiza development [95], and may inhibit disease organisms [83]. In the study that compared bark to commercial media [83], seedling losses were greatest in commercial media with pHs above 6.0, and losses in- creased as the water-holding capacity of the medium increased. Bark maintained pH and water in a range that limited disease development. However, pine bark also has some disadvantages. Nitrogen deficiency may develop in bark-amended media, causing some researchers to discourage its use [80]. Milled bark in plug-type containers does not bind well with roots and makes extraction difficult. Bark also has low water-holding capacity; for growers to process their own seeds with the small therefore, seedlings need more frequent watering during the laboratory cleaners or aspirators available [25]. (For more growing phase and dry out more readily when outplanted information about seeds, see chapter 4, this volume.) [49]. Until more information is available, bark should be used only as a partial replacement for peat in the growing 7.6.2 Disease Problems medium, and then only if composted first. Current data In the past, fungi borne on southern pine seeds have not indicate that the peat-vermiculite blend is still the most been a major concern because most observations indicated satisfactory (Table 7.4). that these fungi were saprophytic and did not affect A number of commercial growing media are available germination [23]. However, with the advent of container for container seedling production. Almost all of these are culture, it is apparent that seed-borne fungi can be an based on the Cornell mixes, which consist of various ratios important cause of seedling mortality. of peat moss, vermiculite, and perlite [26]. However, these Many seedlots contain infested seeds. For example, 8 to blends have been developed for horticultural and vegetable 20% of the seeds from five longleaf seedlots tested for use and are unsuitable for conifers unless precautions are Fusarium were found to be infested, and all five species of taken to reduce the pH to levels optimum for conifers. Fusarium recovered were pathogenic [82]. Fusarium has Some manufacturers will custom blend and reduce the since been isolated from seedcoats of shortleaf (P. echinata amount of limestone so that pH is more satisfactory; the Mill.), slash, and loblolly pine seed [84]. Pathogens may advantage of peat-vermiculite mixes without limestone also be present inside pine seeds [79]. Such infected seeds over commercially blended peat-vermiculite mixes (Jiffy germinate poorly, and damping-off losses are increased. In Mix®) produced for horticultural use is evident (Table addition to Fusarium, Mason and Van Aarsdel [67] have 7.4). Although nutrients in Cornell-type mixes are suffi- identified Trichothecium as a pathogen on loblolly pine cient for the first several weeks, supplemental fertilizers seeds. must then be added. Microorganisms infesting conifer seedcoats can be controlled by surface sterilizing or coating with fungicides. Techniques for using seed sterilants and fungicides on 7.6 Seedlot Selection southern pine seeds were reviewed by Barnett and Brissette [19]. (For more information on insects and diseases, see 7.6.1 Collecting and Processing Seed chapter 20, this volume.) The high-quality seeds essential for growing container seedlings are obtained when cone and seed collecting and 7.7 Environmental Controls processing are carefully controlled [9]. Complete removal of unsound seeds should be specified when seedlots are The degree of environmental control needed to produce purchased; when seedlots are small, it is often convenient southern pine seedlings depends on whether they are grown n r t f ph th th n r l r n n. F r d l n r n n ph , n nv r n nt l ntr l n r th pr r n rn r t v d v rh t n dl n r n n r nh nd t pr v d d t l t r . F r dl n r n t f ph , th l v l f l ht, t r , nd t p r t r t ll b nt n d th n pt bl r n . Th f ll n d n pr r l n r l d t th nv r n nt l nd t n r lt n n b t r n t n nd dl n p rf r n f th th rn p n . D t l d d r pt n f p nt nd f l t r v l bl n T n nd D n ld 0 ].
. . r n t n P r d F r .6. r n t n f th rn p n d t f v d r n t n d p nd n d t l ht nd t p r t r f ll n pr r n t n tr t nt ( d pt d fr B rn tt ] . t r nd f v r bl t p r t r . Th l f pt r n t n nd t n n b ff t n p b h v n tr t f t n r r nt , b t n tr t f d d l n th n n th tr t f t n p r d. F r x pl , l bl ll r n t d ll nl t 8° (6 °F nd 24° ( °F (F . p n r n t n r pr pt nd pl t nd r .6 . Th r p n f l h, l bl ll , nd h rtl f d t l t d f ld nd t n 6° (60°F , h r ph t t p r t r r l r (F . .6 th t p r t r t p r d] h n th tr t f t n t n r d fr 0 h h n tr t f d d f th thr p r h d p d t 4 r 60 d . r n t n 24° . n tr t f d l h p n d r l ff t d b t p r t r xtr th n r n . . . L ht tr t f d l bl ll r h rtl f d . tr t f d l h p n th rn p n d r r l ht f r r n t n 6, 8 , d h d d r n , 8 t 2 ° (6 t 8 °F , t h h ]. H v r, th nt n t f th t l ht r l t v l r n t n > 0%. n p rt nt l h nd l bl ll p n d r n t Th b v d t ] r bt n d nd r t nd rd ll t ,600 l x ( 0 f t ndl t ,200 l x ( 00 l b r t r nd t n th n t nt t p r t r . dd f t ndl 0]. n t d, t th l n th f th t n l v l t n r d th fl t t n t p r t r ph t p r d th t n r ll p rt nt. lth h l h th t b tt r r pr nt t l nd t n . L n l f p n p n r n t ll ll nd r 8 , 2 , nd 6 h r th nl n f th f r p dv r l ff t d b ph t p r d , l bl ll p n r n t b tt r h n th t p r t r lt rn t n b t n 24° ( °F nd ° ph t p r d n r d fr 8 t 6 h r . ( °F (T bl . . f n ll l r h h t p r t r r nt p t d d r n th r n t n p r d, r f r t r . . .2 t r n f r t f r n t n d r d, th n th p r d f nt n r t b t r d fr ntl d r n th tr t f t n h ld b l n th n d. F r l bl ll nd r n t n p r d. Th f r f th pr n l r pr t h rtl f p n , tr t f t n f r 4 t 0 d n t nl n t d l d th d fr d r t nt t th t h t n r n t n v r th t f th t nd rd 0 d d . h n t n t d, th t h ld tr t nt, b t l r lt n b tt r r n t n nd r n t b l ht t ll th p tt n xt r t dr t th dv r nd t n , ]. b tt f th nt n r. ntr l f r t r n t th t r fl t nv r n nt l h n , h th t t ® ], r r d r bl th n t l th t t r n T bl . . r n t n f th rn p n d nd r v r pr d t r n d h d l r rdl f n d. t p r t r r . D r n th r n t n p r d, th t r nt nt f th p tt n xt r h ld r n n r f ld p t . n t r tr b nd —2. b r ( 0.2 P r d r n t n f th rn p n ]. Th r v r t n n p nd r dr r nd t n , h v r r n t n f l n l f p n b tt r th n th t f l h p n d t t r tr f —8 t — 4 b r ( 0.8 t — .4 P .
. . . T p r t r r n t n r p n f th rn p n d t t p r t r v r b p , dl t, nd b th nd l n th f tr t f t n ]. t l n l f p n dl t Figure . . D v l p nt f l n l f (LL nd l bl ll (L p n dl n t d ff r nt r n nd r th r f ll n r 0 t 0% h d ( d pt d fr B rn tt 8] .
. .2 P t r n t n P r d being used operationally in Canadian container nurseries, stimulates early budset and frost hardiness. 7.7.2.1 Light Otherwise, shading is used commonly to help control Photoperiod can either be lengthened or shortened, excessive temperatures, particularly in late spring and depending on the type of facilities available. Extending the summer. By reducing incoming solar radiation, shadecloth photoperiod with low-intensity light at intermittent can lower greenhouse temperatures 5°C (9°F) or more. intervals generally produces larger seedlings during winter Recommended levels of shading have ranged from 30 to when natural photoperiods are relatively short. An extended 55% [109]. But recent results have shown that seedling photoperiod can prevent early budset, lengthen internodes, development, particularly of longleaf pine, is markedly increase foliage size, and promote earlier change from affected by the shading [18]. Longleaf seedlings grown at primary to secondary needles. 30 and 50% shade were significantly smaller in stem Limited data are available on the effect of an extended diameter, top weight, and especially root weight (Fig. 7.7). photoperiod on southern pines. However, ponderosa pine Loblolly seedlings followed the same trends as longleaf, ( . ponderosa Dougl. ex Laws.) seed sources from 33° N but the magnitude of differences between sun and shade latitude (about the latitude of Dallas, Texas; Jackson, exposures was not as great. Mississippi; and Savannah, Georgia) are quite photo- These results have strong implications for producing sensitive [108]. Seedling height growth and dry weight longleaf pine in containers. Growing longleaf seedlings in were increased when the photoperiod was extended by full sun, or at the lowest level of shade possible, is highly incandescent lighting at intensities of 270 lux (25 foot- desirable. The best way to apply this technology is to sow candles) for 1 minute out of every 30 during the night. seeds in containers in late spring (May or early June) and Because short days are important in developing cold grow them in the open throughout the summer. Seedlings hardiness, some growers shorten the photoperiod by with larger diameters and (perhaps more important to field covering the greenhouse with black cloth part of each day performance) greater root systems are then available for during late summer or early fall. This technique, which is planting in late summer or fall. Not only are seedlings of b tt r l t , b t th r pr d d r n ll ld 40] f r dl n > 6 nth ld. pp r ntl , b r nh tr t r n t r r d. lth h dl n d v l p, th t p r t r pt f r r th t ppr pr t f r l n l f p n , th t hn l b n f t h ft. l bl ll nd th r th rn p n ll. B t 22] l r p rt d th ff t f v r n d n ht t p r t r b n t n n d v l p nt f nt n r . .2.2 t r r n l n l f p n dl n . D n ht t p r t r f H v , nfr nt t r n h ld h r t r z th 2 ° ( 6 °F pp r d t b th b t b n t n f r p t r n t n p r d. h r ll th rf n r n d n dr ht, h r t r t p rt nt f th d t dr b t n t r n nd r d th f r f l h ndl n nd pl nt n . r r t p r t r h n f d p n ff. L fr nt t r n l l r r lt d n b tt r t p pp r n b t pr d d r, th t r nt nt f th d , h h n r r t n, f n r r t . b rpt n f n r l , nd r t r th. lth h h tr t t p r t r ntr l n t p bl nd r p r t n l nd t n , r r h ld b r f . .2. T p r t r th p rt n th t d rn l t p r t r fl t t n h v f dl n r t b pr d d d r n nt r, h t d f r dl n r th. r nh ll b r r d. H t n b pr v d d th r v rh d r nd r dl n b n h . r nh t l b l d d r n r th r t pr v d pt .8 lt r l Pr t r n t p r t r . v p r t v l n n n r nh t l z n xh t f n nd tt d p d r l v Th lt r l t hn n r t pt z r th r h d n n l h lp nt n l r t p r t r . nd l t f nt n r dl n r n t ll nd r T n nd D n ld 0 ] pr v d th r h d n t d th r f r b r r t t . Th f ll n f v r t f r nh h t n nd l n . d r pt n f lt r l pr t nt nd d t pr v d th H v r, lth h n r r h v r h d f r f r t r th nf r t n t h rt n t hn r p f pt t p r t r f r r th, th pl x d nd h th ff t dl n l t . r l t n h p b t n t p r t r nd r th d t r n n pt d ff lt. .8. F ll n nt n r D nd n ht ph f t p r t r r , nd th T pr d n f r r p, th nt n r t b f ll d d ff r n b t n th , h v b n f nd t ff t n f r l , h v t h ld n th v l f r th. r r 2] bj t d r ld l bl ll d r n d ttl d t th l v l. B f r n l n t v r d nd n ht t p r t r b n t n . t n r r f ll d, th d h ld b t n d th t t H r p rt d th t r th f h t n r d th r n d n t d t b t d n t l p. l htl t d t p r t r nd d r d th n r n n ht t p r r t h ndl , f ll r n f r l , nd n b tt d t t r . Th d ff r n b t n d nd n ht t p r t r f ld p t r r d l th n dr d . pp r d t b th t p rt nt f t r h dl n nt n r n b f ll d b h nd r h n . Th r t ll t h n th d ff r n b t 2. ° (22°F pl t h nd th d t t n b r f bl r tr nd h rt t h n th r n d ff r n . P rr 8 ] l n p v d rf nd h v l t pr d d v r r p rt d n r ll n r d h ht r th f l bl ll d th t p. n x n b pt ff nd d f r th n xt l n th n r n d t p r t r . r th th d b t h. T ttl th d , h bl r tr h ld b t p r t r f 2 ° ( 4°F l t f r n ht t p r dr pp d fr h ht f t 0 (6 t 2 n. t r t r r n n fr 20 t 26° (68 t °F nd h h t f r thr t . Th nt n r n th n b t pp d ff. Th n ht t p r t r r n n fr 0 t ° ( 0 t 6 °F . h ld b t r d b f r d n t ttl th d n n f th t xt n v t d f t p r t r b l th nt n r t p nd t n r th t th d ff t n l bl ll dl n r th, r n ld 40] t. h n r v l bl th t ll ll t nt r d h t h ht nd dr ht f h t nd r t f d t b d p t d nt nt n r p n n h n dl n r 6 nd nth ld. 2 ° ( 6 nv r. Th h n ft n v br t th nt n r t °F d n ht b n t n pr d d x h ht ttl th d . r th nd h t dr ht, th r p d d r thr h 26 20° ( 68°F t l t 2 2 ° (84 °F . t .8.2 n T hn B t 22] t d th t nt n r l bl ll dl n r n f r p r d f b t 2 h ld b bj t d t .8.2. N b r f d p r nt n r 2 2 ° (84 °F d n ht t p r t r f r 4 t 6 , dl t th l r n t n r r lt pl d n th n 26 20° ( 68°F r 26 ° ( 6 °F f r th t r d th n b r f v nt v t . n th th r h nd, r n n t . Th r ld t dv nt f th nt n r th x dl n ll t b th nn d. f t t rt, b t ld l h t r th h l nt n n T h lp n z th pr bl , P pp r nd B rn tt 88] h h t t l ht. B t 22] pt t p r t r f r t n h n h h v r n n b r f dl n nth ld r t d ff r nt fr r n d r n p r v t . F r n t n , 0% f th containers could receive three seeds, 20% two seeds, and inoculum may be scarce or lacking [14, 15, 30, 32, 39, 61, the remaining 50% one seed. Mixed sowing schemes are 62]. Therefore, it is important that root systems of container generally more cost-efficient than the standard constant- seedlings destined for such sites be inoculated with number approach but still require some thinning to achieve mycorrhizae before they are outplanted. one seedling per container. Marx and his coworkers [63, 66] have developed techniques to produce mycelial inocula of Pisolithus 7.8.2.2 Sowing methods tinctorius in a vermiculite culture. These techniques have Methods of seed sowing vary from hand seeding or use made it feasible to propagate and manipulate this fungal of simple templates to elaborate seeding machines. Many symbiont. A simple and less expensive means of container operations use some type of vacuum seeder, inoculation with P. tinctorius is through basidiospores, the which consists of a seeding head, connected to a vacuum primary agents for disseminating many ectomycorrhizal cleaner or pump, with holes drilled to match the container fungi. Several workers have used spores of specific fungi as arrangement. Even the most efficient seeders occasionally inoculum for synthesis of mycorrhizae on pine [65, 105]. leave blank containers, so growers should visually check Pisolithus tinctorius produces large basidiocarps (puff the cavities. balls) that contain billions of spores. Spores are usually mixed with the peat-vermiculite medium before containers 7.8.2.3 Seed covering are filled, but Theodorou [105] found that coating seeds of The effect of covering southern pine seeds varies with Monterey pine (P. radiata D. Don) with freshly harvested the type of watering regime used [117]. Germination is basidiospores was an easy, effective way to introduce usually most complete and rapid when seeds remain mycorrhizal fungi into soils. International Forest Seed uncovered and are watered by a misting system [11]. If Company of Birmingham, Alabama, has a commercial seeds are watered less frequently, a seed covering, typically process for pelletizing southern pine seeds with P. a layer of medium, facilitates germination through a tinctorius spores. After pelletized seeds are sown, the mulching effect that retains water near seeds. In general, container should be drenched with water to ensure that the larger seeds can be covered to a greater depth than smaller inoculum is washed from the seedcoat; otherwise, the pellet ones. may inhibit germination. Perhaps the greatest problem in using spores for mycorrhizal inoculation is the lack of a 7.8.2.4 Mycorrhizal inoculation technique for evaluating spore viability. Mycorrhizae are the structures resulting from the Inoculation of the container growing medium with colonization of a host root by a suitable fungus. They mycorrhizal fungi necessitates some modification of the increase availability and absorption of nutrients, especially normal cultural regime. As previously stated, the high phosphorus, which is often the most limiting nutrient on fertility levels should be reduced about one-half, to Coastal Plain sites in the South. Ectomycorrhizae also encourage mycorrhiza development [62, 64]. The use of protect fine absorbing roots from being attacked by fungicides, which can be either harmful or beneficial to pathogens [60]. On sites without natural populations of mycorrhiza development, should be monitored. Pawuk et mycorrhizal fungi, pines will not survive or grow well. al. [87] evaluated the effects of seven fungicidal drenches Indeed, the benefits of having visible mycorrhizae on the on development of P. tinctorius and T. terrestris mycor- root systems of bareroot seedlings when they are outplanted are well documented [61]. T bl .6. ff t f f n d tr t nt n t rrh z Development of some species of mycorrhizal fungi may d v l p nt n l n l f p n dl n r n n l th be limited on heavily fertilized seedlings [62, 64], and less t n t r nf t d nd rb rn nf t d (pr r l b fertilization — about one-half of what would normally be h l ph r t rr tr d (fr P t l. 8 ] . considered optimum — may be necessary to encourage mycorrhizal inoculation. When container nurseries are located near forested areas where airborne mycorrhizal spores are abundant, natural inoculation may be sufficient. Barnett [15] found that Thelephora terrestris developed on seedling root systems in containers from airborne spores, and high fertility did not seem to inhibit its development. Evaluations of the field performance of shortleaf and longleaf seedlings indicated that initial seedling size was more closely related to growth than amounts of mycor- rhizae on roots [15]. Considerable evidence suggests that inoculation with mycorrhizae improves seedling performance on difficult sites such as arid soils, reclamation areas, and pine plantings in the southern Great Plains where natural rhizae on roots of container longleaf pine. The degree of ing, with control seedlings being tallest (Table 7.7). After mycorrhiza development differed significantly among transplanting, only seedlings originating from germinants fungicide treatments (Table 7.6); only seedlings drenched with the shortest radicles were significantly smaller than with Banrot® and Benlate® had greater development than those from all other treatments. Sown seedlings were 1 to 2 the control (no fungicide). weeks older than transplants and therefore larger. Likewise, transplants with long radicles were probably older than 7.8.3 Transplanting and Thinning Ger- transplants with shorter radicles. minants Transplanting should be done once an empty cavity Empty containers can represent a significant loss because becomes evident, usually about 10 to 14 days from sowing. they cost as much as a seedling to maintain through a Although better growth after transplanting is related to growing cycle. On the other hand, growing multiple seed- increased radicle length, it is better to transplant soon after lings per container often reduces seedling quality. These sowing when the radicles are not so long and not so problems are best avoided by careful seedlot selection and susceptible to damage. If transplanting is delayed much proper sowing techniques. However, some situations may beyond 14 days, germinants with longer radicles should be require transplanting, thinning, or both. used because smaller seedlings are quickly suppressed. As a general recommendation, the grower should (1) use However, unless care is taken to avoid damage to the only the best quality seeds available, (2) thin multiple seed- radicles, transplanting of older germinants is generally not lings to one per container, and (3) transplant only vigorous as successful. germinants. Both thinning and transplanting should be completed as soon as possible after germination. 7.8.3.2 Thinning If cavities contain several seedlings, then the grower 7.8.3.1 Transplanting must decide whether or not to thin. Longleaf pine seedlings If 5 to 15% of cavities contain ungerminated seeds, were more seriously affected by multiple seeding than germinants from cavities with multiple seedlings or from loblolly or slash seedlings [19]. The most marked effect germination flats should be transplanted to the empty cells. was on longleaf seedling development, measured as dry Up to 5% empty cells 4 weeks into a rotation will have weight: at the end of 14 weeks, dry weights of multiple- little practical effect on costs. If more than 15% of cells are grown seedlings were reduced by one-half or more. In empty, however, seed should be sown in additional addition, the smaller, multiple-grown seedlings had poorer containers. survival than those grown with only one seedling per Pawuk [85] studied the effect of transplanting on initial cavity. Because longleaf pine seedlings are more intolerant seedling growth and development. Transplanting longleaf than other pines to higher seedling densities [21], multiple pine germinants, regardless of their radicle lengths, is sowing should be minimized and any cavities with more detrimental to subsequent diameter growth compared to than one seedling thinned. growing trees from seed (Table 7.7). Total dry weight of The effects of multiple sowing are less drastic with slash both longleaf and shortleaf pine at 15 weeks was directly and loblolly pine. However, initial seedling development and significantly related to radicle length when seedlings was reduced by multiple seeding without thinning. were transplanted. Control (seeded) seedlings were Although size differences were not significant among heaviest; their average weight was about double that of treatments after 3 years in the field, differences became transplants with short radicles. greater each year — slash seedlings grown one per cavity Height of shortleaf pine seedlings at 15 weeks was were 3% taller than those grown three per cavity after 1 directly related to radicle length at the time of transplant- year but 8% taller after 3 years. No long-term data are available on the effects of planting T bl . . ff t f r d l l n th t t f tr n pl nt n n containers with multiple seedlings; however, results from r th f l n l f nd h rtl f p n dl n ft r 15-year-old multiple-seeded spots indicate the trend [29]: ( d pt d fr P 8 ] . leaving two or more seedlings per spot significantly reduced height and diameter growth relative to one seedling per spot.
7.8.4 Growing-Medium Moisture The effects of different moisture levels on development of loblolly and longleaf pine seedlings were determined by measuring root and shoot dry weights after a 10-week growing period (Fig. 7.8). Peat-vermiculite mixtures with moisture contents between 300 and 500% (dry-weight basis) produced the best seedlings. Growing-medium moisture content can readily be evaluated with the container weighing method [71], which T bl .8. R nd d n tr nt n ntr t n n r n d f r th rn p n ( n l d t d fr 48, , 04, 0 ] .
Figure 7.8. Characteristics of loblolly and longleaf pine d l n r n f r 0 t v r t r nt nt n p t v r l t xt r ( : .
l is useful for monitoring irrigation. When the weight of a filled container declines to some predetermined percent- age of the weight of container when medium is saturated, ppm of B, 0.17 ppm of Mn, 0.02 ppm of Zn, 0.02 ppm of the crop is watered. This percentage is often around 75 to Cu, and 0.003 ppm of Mo [48]. The availability of these 80% of the container weight when medium is at field nutrients is highly dependent on pH of the medium. Growth capacity, depending on the type of container, type of for most conifer seedlings is optimum in the pH range 5.0 growing medium, and species. Container weight must be to 6.0 [53]. adjusted for seedling weight periodically during the growing season. 7.8.5.1 Fertilizer formulations Incorporating slow-release fertilizers into the growing 7.8.5 Seedling Nutrition medium or adding granular fertilizer as a "top dressing" to Information about special nutritional needs of container containers is a common horticultural practice, although the southern pine seedlings is very limited. Fortunately, the use of such techniques in seedling operations is limited range of nutrient concentrations that provide good growth because of the small top-surface area of the container. is quite broad, and most coniferous tree species have Osmocote® formulations have often been incorporated, similar requirements. Macronutrients are needed in and Osmocote 18-6-12 has worked well with southern relatively large amounts; not only is the total concentration pines. However, incorporation may result in overfertiliza- of each macronutrient element important, but also the tion and limit the grower's ability to stop height growth and relative proportion of each. Micronutrients (or trace harden seedlings when desired. This may be less of a elements) also are critical to seedling growth but are only problem when spring outplanting is anticipated and the needed in very small amounts. Recommended concentra- need for hardening is not as great. tions of macronutrients and micronutrients for southern Most seedling operations use commercial soluble pines are summarized in Table 7.8. fertilizers, which are dissolved in water and injected into The six macronutrients - nitrogen (N), phosphorus (P), the irrigation system or sprayed over the trees by hand. potassium (K), calcium (Ca), magnesium (Mg), and sulfur These fertilizers, produced by a number of manufacturers, (S) - have been studied in some detail. In one study [104], are available in numerous types, formulations, and recommended nutrient levels for bareroot southern pine proportions of macronutrients and micronutrients. Peters nursery soils were 25 to 38 ppm of P, 75 to 100 ppm of K, Peat-lite Special® formulations work well with southern and 300 to 600 ppm of Ca. In another study [73], growth of pines grown in peat-vermiculite media. Some fertilizer slash pine in sand culture was best when concentrations of manufacturers offer custom formulations based on their N and K were both > 125 ppm but < 625 ppm. According analysis of local water samples and crop needs. to literature on other conifers, concentrations of Mg should Growers can also custom-mix nutrient solutions by range from 15 to 73 ppm, of S from 20 to 150 ppm [109]. adding various amounts of technical-grade chemical Work with the micronutrients iron (Fe), boron (B), components to water according to the optimum nutrient manganese (Mn), chlorine (Cl), zinc (Zn), copper (Cu), and regime for the species, potting mix, and water composition. molybdenum (Mo) has been extremely limited. Recommen- Tinus and McDonald [109] developed a format for dations for Scots pine (Pinus sylvestris L.) and Norway determining the chemical formulation best suited for an spruce [Picea abies (L.) Karst] are 0.93 ppm of Fe, 0.17 individual nursery situation. Rhizoctonia is a common soil fungus that spreads in nature by movement of infected soil or plant debris from one area to another. Though its source is unknown, it could easily be brought into greenhouses, like other soil fungi, by workers or on tools and equipment. Rhizoctonia has been observed attacking seedlings in germination trays in a seed testing lab [84] and on the foliage of container longleaf pine seedlings. In all cases, it developed when seedling foliage was wet for extended periods and spread from seed- ling to seedling, its mycelia clearly visible. Water molds such as Pythium and Phytophthora may enter container nurseries through contaminated irrigation water or by methods previously mentioned. They are favored by wet, poorly drained soils and cause root rot and damping-off of young seedlings. As seedlings mature, they become more resistant, but root development and seedling growth may still be reduced. Some cultural practices can help prevent loss of seed- lings to disease. The medium should be pathogen free from the start and well drained. Seedlings should not be over- watered. Several available fungicides, if applied promptly and correctly, will control damping-off and root rot; however, there is no one fungicide cure-all. Figure 7.9. Effects of timing of initial fertilizer applications and dry weights of loblolly pine seedlings grown for 20 weeks. 7.8.6.2 Foliage diseases and rusts Foliage diseases have not been a problem on container 7.8.5.2 Timing and initial application southern pine seedlings, probably because of the short Traditionally, adding nutrients during germination has period necessary to grow plantable seedlings and the not been recommended because they are supplied by the absence of prolonged periods when foliage is wet. The seed and may increase losses due to damping-off fungi same can be said for the rusts, although seedlings could be [109]. Fertilization is usually scheduled to begin after infected with Cronartium rusts and symptoms would cotyledons have shed their seedcoats (about 3 weeks). probably not be observed before seedlings were shipped. However, this delay can substantially affect seedlings, for The possibility of rust infection should not be over- example, reducing loblolly pine seedling development by looked. Spraying with fungicides to prevent rust infection nearly 20% (Fig. 7.9). If the crop is on a short rotation, is not necessary in closed greenhouses. However, during however, fertilization at the time of seeding may be spring, seedlings should be watered early in the day so desirable. Even if germinants cannot effectively utilize foliage is dry by night, especially during wet weather when nutrients at this early stage of development, those nutrients rust spores are released. Pawuk [84] observed rust infection are available as soon as they are needed, which may hasten on slash pine seedlings in an experimental greenhouse in growth. If a short growing period is not critical, delaying Louisiana. Seedlings were purposely watered in the fertilization until after germination may be beneficial from evening so foliage would be wet overnight to favor rust a disease-management viewpoint. infection. Infection was only 3%, compared to 65% for seedlings similarly treated and grown in an adjacent, open .8.6 P t n nt shadehouse. The low rate of greenhouse infection was probably due to the absence of sufficient inoculum, since 7.8.6.1 Soilborne diseases air movement into the greenhouse was minimal. As long as Species of Fusarium especially F. moniliforme, are the foliage remains dry and greenhouses are closed at night, fungi most commonly cultured from diseased seedlings and rust should not be a problem. When container seedlings are growing media [84]. Fusarium has been cultured from air grown or held outside, seedlings should be sprayed to avoid and water samples in and around greenhouses, but always rust infection. at low levels; most of these fungi probably are spread from infected seedlings during watering. Fusarium often 7.8.6.3 Algae produces abundant spores on infected seedlings; once Many blue-green and green alga species develop on spread to the soil, infection builds up over time. Ap- container growing medium [12]. Once algae dry, a crust parently, seedlings become more resistant to infection as develops, creating a barrier that interferes with irrigation, they mature. (For more information on pest management, fertilization, and pesticide application [109]. One effective see chapter 20, this volume). algae control is a perlite or grit covering on the surface of Table 7.9. Alga development on shortleaf pine seedlings grown in hard-to-reach places, such as between and under in containers drenched with Maneb® and Dichlone® (adapted benches, should be treated with nonvolatile, broad- from Pawuk [86]). spectrum herbicides such as simazine; however, any herbicide should be very carefully applied in a closed greenhouse. Generally, weed problems can be minimized by controlling weeds close to the greenhouse and through proper sanitation.
7.8.6.5 Rodents Mice are considered the principal pest; they can eat or cache large numbers of seeds from containers in a short time and can also clip young, succulent seedlings. The main defenses are construction of physical barriers, minimizing rodent cover, and trapping or baiting. Production areas should be free of debris or plants that will shelter or provide food for rodents. A greenhouse should be tightly enclosed at the base, and all doors should automati- cally close when released. Elimination of any habitat for mice, combined with barriers to greenhouse entry, will usually prevent serious rodent problems. Some limited trapping or baiting may be necessary, however. Warfarin@ as treated oat bait is the most commonly used rodenticide at present [109].
7.8.6.6 Insects Most common insect pests, such as grasshoppers, ants, and caterpillars, are not serious threats to seedling culture and can usually be controlled by sanitation, barriers, and the growing medium. However, because this may affect baiting. Serious insect pests, including aphids, whiteflies, seed germination, chemical control of algae may be scales, thrips, and mites, typically enter the greenhouse desirable. through the ventilation system. Under greenhouse Chemicals that control algae in water are not labeled for conditions, these insects can reproduce rapidly and cause treatment of growing media, so the greenhouse manager extensive damage. Large insects occur less frequently; has no guidelines for selecting appropriate chemicals to more obvious, they are easier to identify and control. treat the soil. In a greenhouse screening study, Pawuk [86] If harmful insects are present, approved insecticides reported that both Maneb® and Dichlone® reduced alga should be used to eradicate them. If management is alert development (Table 7.9). Alga control was better when and observant, the "see, identify, and treat" program should fungicides were applied at either weeks 3 and 8 or at week be best. The mode and timing of application and the 5 alone than when applied at week 3 alone. At each drench chemical used should be designed for the target insect. (See schedule, alga development decreased as Maneb concentra- also chapter 20, this volume). tion increased, a trend absent from the Dichlone treatments. Neither Maneb nor Dichlone inhibited the growth of 7.8.7 Controlling Seedling Morphology shortleaf pine seedlings; indeed, growth was greater in many treatments, especially Maneb, than in the control. 7.8.7.1 Shoot morphology and budset Maneb and Dichlone may also have protected the seedlings Top pruning of container seedlings is normally not from pathogenic soil fungi. necessary and cannot be routinely recommended. However, when seedling development has not been adequately 7.8.6.4 Weeds controlled by cultural regimes, pruning may be desirable to Where sterile growing media are used and tree seed is obtain a better seedling balance. It may be beneficial to clip weed free, weeds in the containers should not be a problem. the needles of longleaf pine to allow all seedlings to be However, outside production areas and greenhouses with uniformly exposed to light; even at low seedling density, gravel floors can develop a considerable growth of weeds, needle development in containers can be so great as to and weed seeds from the air or outside production areas can cause shading problems in this very intolerant species. be drawn into greenhouses through the ventilation system Needle clipping or top pruning reduced initial seedling or carried in on workers' feet, germinating on floors or in size and weight of longleaf, loblolly, and slash pine (Table containers. Because weeds may harbor other pests, any that 7.10). Clipping longleaf needles did not improve seedling germinate should be removed by hand. Those that develop field performance; but of the clipped seedlings, those that bl . 0. Eff t f t p pr n n nd n dl l pp n th rn p n dl n n n t l d v l p nt nd f ld p rf r n [ ].
were clipped early performed best. For all three species, applied to container walls will stop root growth at that wall. pruning did not markedly improve field survival or growth; With this technique, a small amount of copper carbonate in fact, field growth 2 years after outplanting was closely (30 to 100 g/L) is mixed with acrylic latex paint, and the correlated (0.967, 0.956, and 0.923 for longleaf, loblolly, inside of the container is painted with the mixture before and slash pine, respectively) with seedling size at outplant- being filled with medium. When seedling root tips reach ing [17]. Hence, the larger seedlings performed as well as the container wall, many of the lateral roots stop growing, or better than those pruned. instead of turning and continuing to grow down the walls to the root egress hole. The laterals that stop often develop a .8. .2 t rph l series of secondary roots, which also stop growing at the Early results from container-seedling studies showed the container wall. Upon removal from the container, these root desirability of restricting root egress from the container tips resume growth outward from the sides of the root during the culture period. Copper paint [97] or screening "plug," promising better lateral root anchorage and access [20] inhibited root growth from the bottom of containers, to water and nutrients. However, extraction from the increasing seedling survival. However, allowing roots to air container becomes more difficult because there are fewer prune when they grow out of the container was found to be roots on the plug surface to bind the medium together. a more efficient means of eliminating root growth from McDonald et al. [72] also evaluated some synthetic auxin containers. The key to effective air pruning of roots is compounds that gave results similar to those for chopper providing easy air access around the container drainage carbonate. holes. Root spiraling, the most prevalent problem for southern pines in containers, can largely be eliminated by .8.8 nd t n n dl n proper container selection. Although a vertically oriented Most seedlings will cease height growth and set bud root system is common in plug-type containers, the rapid when exposed to moisture stress and short photoperiods. root growth from the lower portion of the plug does not Reducing the nitrogen provided to seedlings also helps to seem to result in root deformity. In fact, it probably slow growth. Although the ease with which growth is improves seedling survival and growth on adverse sites stopped depends upon the season, it can be stopped any [16]. However, the early development of roots from the time of year. The length of time allowed for the initial bottom of plugs may slow mycorrhiza development; the hardening stage, during which growth ceases, stems lignify, microenvironment and soil associates of these more and buds set, depends on the environmental conditions vertically egressed roots are not as favorable as those expected at the time of outplanting. surrounding more laterally developed roots nearer the soil surface [94]. .8.8. M t r tr Certain techniques can change or control the pattern of As seedlings approach the desired size, moisture level of root morphogenesis in plug-type containers. Burdett [28] the growing medium should be allowed to decline to begin has reported that copper carbonate in acrylic latex paint the hardening process. Midday plant water potential should be reduced to between -12 and -15 bars (-1.2 and -1.5 MPa) proper physiological condition on the required shipping to impair height growth and help initiate hardening. The date. A growing schedule shows the environmental time required for plant water potential to drop to the desired conditions surrounding the seedling at any given time (Fig. level depends on moisture content of the growing medium 7.10). By reading the season line and estimating the time and evaporative demand. needed for each of the indicated management activities Water status can be evaluated indirectly by weighing beneath it, the grower can estimate the periods for the containers to determine moisture content or directly by different growth stages. The time required for each stage measuring plant water potential with a pressure chamber. can be easily determined if the nursery manager has growth Weighing is appropriate while the seedlings are small and curves and a table of optimum conditions for the desired water represents a major portion of their total weight; a species. pressure chamber is recommended for larger seedlings. To maintain plant moisture stress at safe levels, careful monitoring of water potential is important. . 0 Pr p d d t p
7.8.8.2 Nutrition We have insufficient data to specify target characteristics Once the seedlings have reached about 80% of the for the ideal container southern pine seedling — that is, the desired height [about 13 cm (5.5 in.)], reducing the nitrogen ideotype. Our best information is for loblolly pine, but it is concentration in the fertilizer solution helps to slow stem from studies not designed to provide predictive equations height growth. The frequency of nutrient applications also relating initial seedling quality to field performance. should be reduced. An increase in rates of phosphorus and However, these data will give some indication of the potassium may foster continued root and stem diameter relationship between morphology and growth. growth [109]. Yet Timmis [106] found that a rather Certain seedling characteristics that relate to field extreme potassium-nitrogen imbalance strongly reduced the performance are easier to measure, and more reliable, than ability of containerized Douglas-fir [ d t nz others. Dry weight and shoot:root ratio are not as easy to (Mirb.) Franco] seedlings to harden. He determined that the determine as is seedling height or diameter. However, K:N ratio must be < 1.0 to permit maximum cold hardening measurement might be simplified because these various after an 11.5-week hardening regime. morphological attributes are related [74]. For example, seed- ling stem diameter at the time of outplanting is closely 7.8.8.3 Cold hardening related to initial height (Fig. 7.11a) but also to seedling Once growth has ceased and stems have lignified, height in the field roughly 2 and 3 years after planting (Fig. additional hardening is needed if late-fall or winter 7.11b). Initial stem dry weight correlates well with height outplanting is planned. In this case, seedlings are gradually after outplanting (Fig. 7.11c); initial height correlates with exposed to more severe conditions, primarily low tempera- height in the field roughly 1, 2, and 3 years later (Fig. tures, that will bring about physiological changes enabling 7.11d). the trees to tolerate the new conditions. Temperatures of 1 The correlations of seedling diameter, stem weight, and to 5°C (34 to 41°F) generate considerable cold hardiness. height at the time of outplanting in Figure 7.11 all indicate Mexal et al. [78] found that approximately 42 days of that, within the range of the data, field performance hardening are required to induce sufficient cold hardiness improves as seedling size at outplanting increases. in an Arkansas source of loblolly pine to enable seedlings However, these results reflect a limited range of initial seed- to survive late fall and early winter outplanting. When soil ling heights — from 7.6 to < 23 cm (3 to 9 in.). Undoub- moisture is adequate, partially hardened stock may be tedly, a point exists after which larger seedlings do not planted successfully in September or October. Seedlings result in greater field growth. Additional data with initially can be hardened by exposure either to low temperatures or taller seedlings (18 to 33 cm) suggest no correlation to short photoperiods, but exposure to low ambient between initial and field heights. Thus, there are practical temperatures and decreased fertilization are the most biological, as well as economic, limitations to how large feasible cultural practices (see also chapter 8, this volume). seedlings should be at outplanting. As long as the type of container and cultural treatment remain constant and produce good-quality seedlings, height . r n h d l at the time of outplanting seems to be the best single morphological indicator of field performance. In addition, The "growing schedule" is a chart of the conditions to be it is easily measured. Other visual criteria, such as presence maintained and operations to be performed as a function of of secondary needles and woody tissue, should also be calendar date from seed preparation to shipment of seed- considered. Additional information clarifying, for example, lings from the nursery [109]. As a planning aid, it should the relationship between morphology and field performance incorporate much of what is known about the growing of a as it is affected by site quality is needed so that container particular crop and the hardening required to have it in seedling ideotypes can be more accurately defined.
F r . . R l t n h p f v r rph l l ttr b t f l bl ll p n dl n t rv v l nd r th n th f ld ( d pt d fr lvr nd B rn tt 4] .
7.11 Handling and Planting and handling if extracted seedlings are not completely dormant and cold hardy [551; that is, succulent, extracted 7.11.1 Extraction from Containers container stock can be planted if handled carefully but How stock is handled before planting depends on the should not be stored. type of container. If seedlings are grown in tubes or blocks, For seedlings shipped in their containers, the shipping they are shipped and planted in their containers. If seed- and storage volumes are considerably greater and include lings are grown in plugs, growers must decide whether to empty cells, only seedling shoots can be graded, and extract the seedlings from the containers before shipment. containers must be returned to the nursery, which is For plug seedlings extracted before shipping, the expensive and invariably damages some of the containers. required shipping and storage volumes are considerably Although root plugs will be maximally protected, succulent less. Seedling roots as well as shoots can be graded, and shoots must still be carefully handled. there are no containers to return to the nursery. However, For economy and efficient use of space, trucks or trailers stock quality can be seriously impaired during cold storage should be fitted with racks or stacking pallets [41, 58]. Seedling boxes must be designed for proper stacking 7.11.3 Site Suitability strength and seedling size. At the nursery, pallets can Several environmental factors that will affect planting usually be loaded onto trucks with a forklift. At the success must be considered before planting container seed- planting site, unloading requires the truck or trailer to be lings, especially on adverse sites or outside the normal fitted with a hydraulic tailgate and small swiveling crane. planting season: soil characteristics such as texture, Truck and trailer beds used for seedling transport must be moisture, and nutrient availability; degree of site clean and clear of gasoline, diesel fuel, pesticides, and preparation; probable air and soil temperature at planting sharp implements; these items can kill or injure seedlings, time and during seedling establishment; competition for tear seedling boxes, or damage containers. (See also moisture and light; and seedling pests [47]. chapter 16, this volume, for more details on care and Available soil moisture is the most critical factor in handling of stock.) evaluating a site's suitability for planting. Soil texture and moisture content determine the soil water potential, which 7.11.2 Care of Seedlings in the Field is a measure of the availability of soil water to plants. At Intermediate storage of seedlings between the nursery field capacity, soil water potential is about —0.3 bars and the planting site should be avoided. Prompt planting, (-0.03 MPa). As soil moisture becomes less available, soil especially when seedlings are not hardened, is often the key water potential becomes more negative. A planting site to reforestation success. However, temporary storage, should be considered high risk if its soil water potential is either en route or at the planting site, is common because of —10 bars (-1.0 MPa) or less [47]. Soil water potential can weather or changes in planting schedules. If seedlings are be best estimated by obtaining predawn pressure-chamber shipped in a refrigerated vehicle, that vehicle makes an measurements of plant water potential from established excellent temporary cold-storage facility. If refrigerated vegetation on the site. storage is not available, a simple lean-to, an unheated barn, Pressure chamber readings do not, however, indicate the or even a shady spot is better than exposing seedlings to rate at which soil water potential is likely to change. Soil direct sun. Air circulation must be adequate to prevent water potential will decrease more rapidly in sandy soils or overheating. Monitoring the temperature of seedlings hot, dry weather than in clay soils or cool, humid weather. stored in boxes or bags is especially critical; for loblolly With advanced planning, soil-moisture retention curves, pine, temperatures above 27°C (80°F) can initiate mold and which indicate the rate of water depletion from the soil, can decay, and 48°C (118°F) for 2 hours is lethal [112]. (For be developed by a soils laboratory for specific planting more information about seedling handling, see chapters 16 sites or general soil types. Tensiometer or pressure chamber and 17, this volume.) readings can then be used to determine where the current In cold weather, container seedlings must be protected soil-moisture potential of a given site is located on the from freezing. Under natural conditions, seedling root curve, providing an estimate of how much water is systems are well insulated by the soil and do not attain the available in the soil and how long it will last [57]. Such same level of cold hardiness as shoots. However, container detailed evaluation is especially valuable if the intended seedlings waiting to be planted in the field may be sub- planting site is particularly severe or droughty. jected to low temperatures that will be lethal to their roots. Moreover, because cold damage to roots is not as obvious 7.11.4 Planting Techniques as that to shoots, root mortality will not be observed until Despite their bulk and weight, container seedlings are shoots are placed in an environment favorable to growth. In easy to plant by hand or machine because of their an Arkansas study, survival was 50% for container seed- uniformly shaped root systems. Descriptions of available lings exposed to —10°C (14°F) in February, compared to hand-planting tools and planting machines have been > 90% for seedlings from the same crop that were moved compiled by Larson and Hallman [56]. (For more inside before the low temperature [77]. Styrofoam-type information, see also chapter 17, this volume.) containers provide greater insulation from temperature extremes than hard plastic ones. 7.11.4.1 Hand planting Because of the relatively small volume of medium in Container seedlings can be hand planted with conven- which container seedlings are grown, seedlings are very tional bareroot planting tools or with tools designed for susceptible to desiccation and must be protected from the specific container types. Specially designed planting tubes, drying influences of the sun and wind. Extracted and such as the Finnish Pottiputki® and the Walter's gun from packaged seedlings should be handled much like bareroot British Columbia, have been used to plant container stock seedlings; that is, they should be kept shaded and packages at rates twice those of hand planting bareroot stock [2, 114, reclosed once opened and watered if necessary to keep the 115]. These tools work by displacing or dibbling the soil to root plugs moist. Seedlings shipped in the container should make room for the seedling root ball. Although their be thoroughly watered at the nursery and rewatered as effectiveness depends greatly on the soil type and soil necessary to maintain the medium at field capacity until moisture, they work well on midrange soil types such as planting. sandy loams, loams, and silt loams [34]. For clays, tools Table 7.11. Average survival of loblolly pine seedlings planted modified; for intermittent-furrow machines, the holding by two methods in three different soil types [14]. mechanisms for seedlings might need to be changed. (See also chapter 17, this volume.)
7.11.4.3 Planting depth As with bareroot stock, planting container seedlings to the proper depth is important to ensure good survival and growth after outplanting. Container seedlings should be planted deep enough that the top of the root plug is covered with about 1 cm (0.4 in.) of soil. Covering the container reduces drying of the root plug caused by the "wicking effect" of moist growing medium exposed to the air. Planting below the groundline also prevents frost heaving of fall-planted container stock [118]. Care must also be taken not to plant container seedlings so deep that the shoot is covered up, especially during machine planting. Control of planting depth is more critical and can be more difficult with container than with bareroot t b d n d t v d l pr n r seedlings [93]. h rd n n f th d ll h n th h l p n d. r v r nd l , th t l t pr v nt th d ll fr 7.11.4.4 Planting season v n n b f r th dl n n b pr p rl pl nt d. One of the greatest potential benefits of using container nd h ld p r r n l b d f r pl nt n seedlings is that the planting season can be extended. In nt n r dl n nd r p rt l rl ff t v f r t central Louisiana, container seedlings have been planted r n n l r nt n r . throughout the year. For summer-planted loblolly, slash, C r n (r v n l r th th nf r t n and longleaf pines, survival and subsequent growth have th nt n r z d dl n pl r lt n b tt r dl n been good, even under droughty conditions [1, 14]. p rf r n n h v r p t d l . In n , However, winter-planted southern pines must be suffi- l bl ll p n dl n pl nt d n h v lt l l ciently hardened before outplanting. rv v d b tt r h n th pl nt n h l r d r th r Trends in field performance were similar for both th n d bbl d ( bl . [ 4]. In S t h n, C n d , loblolly and slash pine container seedlings outplanted rv v l nd h ht r th f l d p l p n ( n monthly from January to September on a silt loam soil [21]. nt rt l. x d. r b t h n l r The poor survival of loblolly pine planted in January was r v d b f r pl nt n n p t l l th b l attributed to improperly hardened stock. The greater d n t f . r h h r [24]. In b th t d , d average height of bareroot, compared to container, trees of l n pl nt d n d bbl d h l n l ht r t xt r d l r n both species indicates that the bareroot seedlings had l th b l d n t f < .6 p rf r d ll maintained their size advantage at planting throughout the r b tt r th n dl n pl nt d n r d h l . three growing seasons of the study. Wh n nt n r dl n r pr p rl h nd pl nt d, Caution must be exercised if planting under droughty th r r t h ld r nt th dj nt l n p t ll conditions. Soil moisture should be estimated to ensure it is n f r nn r. r 26 pl nt t n n v r l t p adequate for seedling establishment and survival (refer to n Or n nd W h n t n, l f r tr r d p 2 7.11.3); in addition, weather forecasts should be considered t 4 r ft r b n pl nt d pl dl n nd th r t during the normally hot and dry months of late spring, t l f d l n t d n ll nd r d ll nt z n . summer, and early fall. Adequate planning and operational On th 2 dl n x v t d, r d r t r f nd flexibility are essential if planting over an extended season n n v r f f th v l bl z n f th pl is to prove successful. [ 2]. In n r l, r t r p r nl h r l h d b n p t d, r t n p r, r dl n v r r dl r d d b f f t r th r th n l t xt r . . 2 n l n nd R nd t n
. .4.2 M h n pl nt n Reforestation success can best be assured when the M t h n l pl nt r d n d f r b r r t d forester and nursery manager both understand that seedling l n n b d pt d f r nt n r t th nl n r quality and the environment at the planting site determine d f t n . C nv nt n l pl nt n h n b field performance. When evaluating container stock for th r f th nt n f rr r nt r tt nt f rr t p regeneration, both foresters and managers should: nd r ll n ll f d. r nt n f rr * Consider using container seedlings for conditions under h n , nl p r t r t hn ld n d t b which bareroot stock or natural or direct seeding is not expected to do well. 12. Barnett, J. P. 1978c. Forest planting and seeding. Pages * Take advantage of the flexibility of container production 185-187 In McGraw-Hill 1978 Yearbook of Science and methods to tailor the growing period, container type, and Technology. McGraw-Hill, New York. 13. Barnett, J. P. 1979. Germination temperatures for container cultural practices to provide the desired seedling culture of southern pines. South. J. Appl. Forestry characteristics at the intended planting date. 3(1):13-14. * Specify the use of only high-quality seeds in container 14. Barnett, J. P. 1980. Containerized pine seedlings for production to avoid empty cells and minimize transplant- difficult sites. In Proc. Reforestation of Disturbed Sites. ing and thinning, thereby ensuring high-quality, uniform June 9-10, 1980, College Station, Tex. Texas Agric. seedlings. Extension Serv. and Texas A&M Univ., College Station. 15. Barnett, J. P. 1982a. Relating field performance of * Provide the least amount of environmental control containerized longleaf and shortleaf pine to mycorrhizal necessary to produce the required seedling characteris- inoculation and initial size. Pages 358-367 In Proc. 7th tics at the lowest production costs. North American Forest Biology Workshop. July 26-28, * Be aware that the relatively small rooting volumes 1982, Lexington, Ky. Univ. of Kentucky, Lexington. within containers make the timing and application of 16. Barnett, J. P. 1982b. Selecting containers for southern pine cultural practices, especially irrigation and fertilization, seedling production. Pages 15-24 In Proc. Containerized Forest Tree Seedling Conference (Richard W. Guldin and critical. James P. Barnett, eds.). Aug. 25-27, 1981, Savannah, Ga. * Adjust handling and planting methods to the planting U.S.D.A. Forest Serv., South. Forest Exp. Sta., New season and to seedling morphology and physiology. Orleans, La. Gen. Tech. Rep. SO-37. 17. Barnett, James P. 1984. Top pruning and needle clipping of container-grown southern pine seedlings. Pages 39-45 In R f r n Proc. Southern Nursery Conferences (C. W. Lantz, ed.). June 11-14, 1984, Alexandria, La., July 24-27, 1984, 1. Amidon, T. E., J. P. Barnett, H. P. Gallagher, and John Asheville, N.C. U.S.D.A. Forest Serv., Atlanta, Ga. McGilvray. 1982. A field test of containerized seedlings 18. Barnett, James P. 1989. Development of container longleaf under drought conditions. Pages 139-144 In Proc. Southern and loblolly pine seedlings is reduced by shading. Tree Containerized Forest Tree Seedling Conference (Richard Planters' Notes 40(1):23-26. W. Guldin and James P. Barnett, eds.). Aug. 25-27, 1981, 19. Barnett, James P., and John C. Brissette. 1986. Producing Savannah, Ga. U.S.D.A. Forest Serv., South. Forest Exp. southern pine seedlings in containers. U.S.D.A. Forest Sta., New Orleans, La. Gen. Tech. Rep. SO-37. Serv., South. Forest Exp. Sta., New Orleans, La. Gen. 2. Appelroth, S. E. 1971. Planting tube makes it easy to plant Tech. Rep. SO-59. 72 p. Japanese paperpot planting stock in Finland. Forestry 20. Barnett, J. P., and J. M. McGilvray. 1974. Copper screen Chron. 47:350-351. controls root growth and increases survival of containerized 3. Arnott, J. T. 1973. Evolution of the styroblock reforestation southern pine seedlings. Tree Planters' Notes 25(2):11-12. concept in British Columbia. Commonw. Forestry Rev. 21. Barnett, J. P., and J. M. McGilvray. 1981. Container 51(1):72-78. planting systems for the South. U.S.D.A. Forest Serv., 4. Arnott, J. T. 1981. Survival and growth of bullet, styroplug, South. Forest Exp. Sm., New Orleans, La. Res. Pap. SO- and bareroot seedlings on mid-elevation sites in coastal 167. British Columbia. Forestry Chron. 57:65-70. 22. Bates, Maynard E. 1976. Growth responses of con- 5. Barnett, J. P. 1969. Moisture stress affects germination of tainerized southern pine seedlings to temperature and light longleaf and slash pine seeds. Forest Sci. 15(3):275-276. in controlled-environment greenhouses. Ph.D. dissertation, 6. Barnett, J. P. 1974a. Containerized planting - a new Duke Univ., Durham, N.C. 280 p. regeneration technique. Pages 129-133 In Symposium on 23. Belcher, E. W., Jr., and B. T. Waldrip, Jr. 1972. Effect of Management of Young Pines (H. L. Williston and W. E. thiram on seed mold and germination of slash pine seed. Balmer, eds.). Oct. 22-24, 1974, Alexandria, La. U.S.D.A. Proc. Assoc. Off. Seed Anal. 62:91-93. Forest Serv., State and Private Forestry, Atlanta, Ga. 24. Bohning, Russel. 1981. Core dibble reduces impact of soil 7. Barnett, . P. 1974b. Growing containerized southern pines. compaction on seedling growth. Canadian Forestry Serv., Pages 124-128 In Proc. North American Containerized North. Forest Res. Centre, Edmonton, Alberta. Forestry Forest Tree Seedling Symposium (Richard W. Tinus, Rep. No. 24. William I. Stein, and William E. Balmer, eds.). Aug. 25. Bonner, F. T. 1977. Equipment and supplies for collecting, 26-29, 1974, Denver, Colo. U.S.D.A. Forest Serv., Rocky processing, storing and testing forest tree seed. U.S.D.A. Mountain Forest and Range Exp. Sta., Fort Collins, Colo. Forest Serv., South. Forest Exp. Sta., New Orleans, La. Great Plains Agric. Council Publ. 68. Gen. Tech. Rep. SO-13. 35 p. 8. Barnett, J. P. 1975. Containerized pine seedlings thrive in 26. Boodley, J. W., and Raymond Sheldrake, Jr. 1963. wood-fiber blocks. Tree Planters' Notes 26(2):13, 20-21. Artificial soils for commercial plant growing. New York 9. Barnett, J. P. 1976. Collecting and processing methods State Coll. of Agric. Cornell Extension Bull. 1104. 8 p. affect pine seed germinability. Pages 70-72 In Proc. 27. Brown, E. F., and F. A. Pokorny. 1975. Physical and Southeastern Area Nurserymen's Conferences (C. W. chemical properties of media composed of milled pine bark Lantz, ed.). Aug. 17-19, 1976, Mobile, Ala. U.S.D.A. sand. J. Am. Soc. Hortic. Sci. 100(2):119-121. Forest Serv., State and Private Forestry, Atlanta, Ga. 28. Burdett, A. N. 1978. Control of root morphogenesis for 10. Barnett, J. P. 1978a. Advances in container production of improved mechanical stability in container grown planting stock. Pages 167-175 In Proc. 5th American lodgepole pine. Can. J. Forest Res. 8:483-486. Forest Biology Workshop. March 13-15, 1978, Gaines- 29. Campbell, Thomas E. 1983. Effects of initial seedling ville, Fla. Univ. of Florida, Gainesville. density of spot-seeded loblolly and slash pines at age 15 11. Barnett, J. P. 1978b. Covering affects container germina- years. Pages 118-127 In Proc. 2nd Biennial Southern tion of southern pine seeds. Tree Planters' Notes Silvicultural Research Conference (Earle P. Jones, Jr., ed.). 29(2):13-15. Nov. 4-5, 1982, Atlanta, Ga. U.S.D.A. Forest Serv., S th t. r t Exp. St ., A h v ll , .C. G n. h. 2 2 , 8 , S v nn h, G . U.S. .A. r t S rv., S th. p. SE 24. r t Exp. St ., Orl n , . G n. h. p. SO . 0. v d n, W. ., nd E. A. S . 4. C nt n r r n 44. hn, h ll p . 82b. r t l d l n f r d v l p n dl n h p t nt l f r ff r t t n f nn lv n nt n r z d n r r pr r . 00 In r . l n p l . r l nt r t 2 (4 :6 . S th rn C nt n r z d r t r S dl n C nf r n . , . ., nd . . C r . 4. ff r n n p t ( h rd W. G ld n nd . rn tt, d . . A . pl nt n l t r r l t n f nt n r r n t b 2 2 , 8 , S v nn h, G . U.S. .A. r t S rv., S th. nd pl t ff t f ld rv v l nd r th f bl r t Exp. St ., Orl n , . G n. h. p. SO . pr . 88 2 In r . rth A r n C n 4 . hn, h ll p ., nd All n . S th. 8 . l f r t n r z d r t r S dl n S p ( h rd W. pl nt n t p rf r n p r n ft r th th rd n , W ll I. St n, nd W ll E. l r, d . . A . r n n. r l nt r t 4( : . 26 2 , 4, nv r, C l . U.S. .A. r t S rv., 46. l , A. K. . S l t n p t f r r r n n f r M nt n r t nd n Exp. St ., rt C ll n , C l . nt n r dl n . r tr Chr n. :200 202. Gr t l n A r . C n l bl. 68. 4 . t , W n A. 6. S l t n n pt pl nt n 2. r n, . . . C nt n r z d l bl ll p n r t . 84 In r l nt n n th Inl nd pr n f r r n ntr l pl nt n . r l nt r t rth t. W h n t n St t Un v., C p r t v Ext n n 24( : . S rv., ll n. . Ed r n, . W. . t pr v p r r d f r 48. In t d, . 62. M r l nt n tr t n f p n , pr , l f r dl n r th. r l nt r t nd b r h dl n n n tr nt l t n . M dd l nd n 24(2 :6 . S f r n n In t t t , St h l , S d n. ( . 0 4. Ed rd , rr . 4. M th d nd h n f r p. pl nt n nt n r z d tr . 26 2 4 In r . rth 4 . hn n, . 68. rt lt r l nd r lt r l f A r n C nt n r z d r t r S dl n S p d t nd l nd nt . l hn n, 04 ( h rd W. n , W ll I. St n, nd W ll E. Cl v l nd Av ., t n l C t , C l f. l r, d . . A . 26 2 , 4, nv r, C l . U.S. .A. 0. n , . 6 . Eff t f l ht n r n t n f f r t r t S rv., M nt n r t nd n Exp. St ., tr d. Int rn t n l S d t n A . 26( :4 4 2. rt C ll n , C l . Gr t l n A r . C n l bl. 68. . n , . 6 . b d dl n . r t r r . Ed rd , rr . 82. ll t t d pl nt n h n 26: 0 , 8. d v l p nt nd t t n f r nt n r dl n ppl 2. Kr r, l . . S ff t f v r b n t n . 2 24 In r . S th rn C nt n r z d t n f d nd n ht t p r t r nd ph t p r d n th r t r S dl n C nf r n ( h rd W. G ld n nd h ht r th f l bl ll p n dl n . r t S . . rn tt, d . . A . 2 2 , 8 , S v nn h, G . :4 . U.S. .A. r t S rv., S th. r t Exp. St ., . Kr r, . ., nd . . K zl . 60. h l f Orl n , . G n. h. p. SO . r . M Gr ll, Y r . 642 p. 6. G rdn r, A. C. 82. ld p rf r n f nt n r z d 4. Kr , . . 82. E rl r th f b r r t nd p p rp t dl n n nt r r r t h C l b . 2 0 In pl nt t n t v r l t n n r n . r . C n d n C nt n r z d r S dl n S p 66 In r . C n d n C nt n r z d r S dl n ( . . S rr tt, C. Gl r , nd C. . l x n, d . . S pt. S p ( . . S rr tt, C. Gl r , nd C. A. l x n, 4 6, 8 , r nt . p. f Env r n nt, C n d n d . . S pt. 4 6, 8 , r nt . p. f th r tr S rv., Gr t r t . C ntr , S lt St . Env r n nt, C n d n r tr S rv., Gr t r t M r , Ont r . CO C S p r . 0 0. . C ntr , S lt St . M r , Ont r , CO C S . G r, E. C. 60. A t t t pr p t n. l r t p r . 0 0. v. 26( 2 8 :4 48. . nd , h ., nd St ph n E. M n ld. 82. h 8. G d n, 0. C. 6. S r pl nt d l bl ll nd pr n , t r , nd h pp n f nt n r dl n n l n l f p n t b l n t r 0 n r r dl n n th t rn Un t d St t . In r . S th rn C nt n r z d rth C r l n . . r tr 4: 6. r t r S dl n C nf r n ( h rd W. G ld n nd . G d n, 0. C. 80. C nt n r z d l n l f p n d . rn tt, d . . A . 2 2 , 8 , S v nn h, G . l n rv v b tt r nd r f t r th n n r r t n U.S. .A. r t S rv., S th. r t Exp. St ., ndh ll t ft r f v r n n . rth C r l n Orl n , . G n. h. p. SO . r t S rv., l h . t 42. 6 p. 6. r n, hn, nd h rd ll n. 80. E p nt f r 40. Gr n ld, S. M. 2. S nv r n nt l ff t n th r f r t t n nd t b r t nd pr v nt. U.S. .A. r th nd n t rpr n pr d t n f Pinus taeda . nd r t S rv., E p nt v l p nt C nt r, M l , Ocimum basilicum . rt t n, Un v., rh , M nt. r j t rd 8024 2 2. 2 4 p. .C. . rd, r ld. . l nt n tr h n th t r ht. 4 . G ld n, h rd W. 8 . n r t n t n r l nt r t 28(2 : . nt n r r n th rn p n dl n . U.S. .A. r t 8. h , S. A. 82. Alb rt ppr h t nt n r z d S rv., S th. r t Exp. St ., Orl n , . . p. dl n h ndl n . 26 264 In r . C n d n S0 8 .2 p. C nt n r z d r S dl n S p ( . . S n t, C. 42. G ld n, . W., nd . . rn tt ( d . . 82. S th rn Gl r , nd C. A. l x n, d . . S pt. 4 6, 8 , nt n r z d f r t tr dl n nf r n : pr d n r nt . p. f th Env r n nt, C n d n r tr f th nf r n . A . 2 2 , 8 , S v nn h, G . S rv., Gr t r t . C ntr , S lt St . M r , U.S. .A. r t S rv., S th. r t Exp. St ., Ont r . CO C S p r . 0 0. Orl n , . G n. h. p. SO . 6 p. . M nn, W. . . St t nd tl f nt n r z t n 4 . hn, h ll p . 82 . A h t r l v rv f th f n th S th. . r tr : 8 . nt n r z d dl n f r p r t n l r f r t t n h 60. M rx, . . 2. E t rrh z b l l d t rr nt d d t h r r t d ? 2 In r . t p th n r t nf t n . Ann . v. h t p th l. S th rn C nt n r z d r t r S dl n C nf r n 20:42 4 4. ( h rd W. G ld n nd . rn tt, d . . A . 6 . M rx, . ., nd . . Art n. . Pisolithus tinctorius ectomycorrhizae improve survival and growth of pine seed- 76. McLemore, B. F. 1971. Light requirements for germination lings on acid coal spoils in Kentucky and Virginia. of loblolly pine seeds. Forest Sci. 17(3):285-286. Reclamation Rev. 2:23-31. 77. Mexal, John G., and William C. Carlson. 1982. Dormancy 62. Marx, D. H., and J. P. Barnett. 1974. Mycorrhizae and and cold-hardiness of containerized loblolly pine seedlings. containerized forest tree seedlings. Pages 85-92 In Proc. Pages 59-63 In Proc. Southern Containerized Forest Tree North American Containerized Forest Tree Seedling Seedling Conference (Richard W. Guldin and James P. Symposium (Richard W. Tinus, William I. Stein, and Barnett, eds.). Aug. 25-27, 1981, Savannah, Ga. U.S.D.A. William E. Balmer, eds.). Aug. 26-29, 1974, Denver, Colo. Forest Serv., South. Forest Exp. Sta., New Orleans, La. U.S.D.A. Forest Serv., Rocky Mountain Forest and Range Gen. Tech. Rep. SO-37. Exp. Sta., Fort Collins, Colo. Great Plains Agric. Council 78. Mexal, J. G., Roger Timmis, and W. G. Morris. 1979. Publ. 68. Cold-hardiness of containerized loblolly pine seedlings. 63. Marx, D. H., and W. C. Bryan. 1975. Growth and South. J. Appl. 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Thelephora terrestris. Can. J. Bot. 48:197-198. 82. Pawuk, W. . 1978. Damping-off of container-grown 66. Marx, D. H., and S. J. Rowan. 1981. Fungicides influence longleaf pine seedlings by seed-borne Fusaria. Plant. Dis. growth and development of specific ectomycorrhizae on Rep. 62:82-84. loblolly pine seedlings. Forest Sci. 27:167-176. 83. Pawuk, W. H. 1981. Potting media affect growth and 67. Mason, Garland N., and Eugene P. Van Aarsdel. 1978. disease development of container-grown southern pines. Fungi associated with Pinus taeda seed development. Plant U.S.D.A. Forest Serv., South. Forest Exp. Sta., New Dis. Rep. 62:864-867. Orleans, La. Res. Note SO-268. 4 p. 68. Matthews, R. G. 1971. Container seedling production: a 84. Pawuk, W. H. 1982a. Diseases of container-grown southern provisional manual. Canadian Forestry Serv., Pacific Forest pine seedlings and their control. Pages 47-50 In Proc. Res. Centre, Victoria, B.C. Inf. Rep. BC-X-58. 57 p. 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Marx. 1980. controlled environment greenhouses - which is best. Pages Fungicide drenches affect ectomycorrhizal development of 81-85 In Proc. Southern Containerized Forest Tree container-grown Pinus palustris seedlings. Can. J. Forest Seedling Conference (Richard W. Guldin and James P. Res. 10:61-64. Barnett, eds.). Aug. 25-27, 1981, Savannah, Ga. U.S.D.A. 88. Pepper, William D., and James P. Barnett. 1982. Seed Forest Serv., South. Forest Exp. Sta., New Orleans, La. sowing strategies for containerized seedling operations. Gen. Tech. Rep. SO-37. Pages 29-32 In Proc. Southern Containerized Forest Tree 71. McDonald, S. E., and S. W. Running. 1979. Monitoring Seedling Conference (Richard W. Guldin and James P. irrigation in western forest tree nurseries. U.S.D.A. Forest Barnett, eds.). Aug. 25-29, 1981, Savannah, Ga. U.S.D.A. Serv., Rocky Mountain Forest and Range Exp. Sta., Fort Forest Serv., South. Forest Exp. Sta., New Orleans, La. Collins, Colo. Gen. Tech. Rep. RM-61. 8 p. Gen. Tech. 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Tinus, Richard W. 1977. Operating a greenhouse container development and spread of Pisolithums tinctorius nursery. Unpubl. paper presented June 1-2 to West Gulf ectomycorrhizae after planting of container-grown loblolly Forest Tree Improvement Program Contactman's Meeting, pine seedlings. Forest Sci. 29:519-526. Alexandria, La. 95. Ruehle, J. L., and D. H. Marx. 1977. Developing ec- 109. Tinus, Richard W., and Stephen E. McDonald. 1979. How tomycorrhizae on containerized pine seedlings. U.S.D.A. to grow tree seedlings in greenhouses in containers. Forest Serv., Southeast. Forest Exp. Sta., Asheville, N.C. U.S.D.A. Forest Serv., Rocky Mountain Forest and Range Res. Note SE-242. 8 p. Exp. Sta., Fort Collins, Colo. Gen. Tech. Rep. RM-60. 256 96. Ruehle, J. L., D. H. Marx, J. P. Barnett, and W. H. Pawuk. p. 1981. Survival and growth of container-grown and bare- 110. Tinus, R. W., W. I. Stein, and W. E. Balmer (eds.). 1974. root shortleaf pine seedlings with Pisolithus and Proceedings, North American containerized forest tree seed- Thelephora ectomycorrhizae. South. J. Appl. Forestry ling symposium. Aug. 26-29, 1974, Denver, Colo. 5(1):20-24. U.S.D.A. Forest Serv., Rocky Mountain Forest and Range 97. Saul, G. H. 1968. Copper safely controls roots of tubed Exp. Sta., Fort Collins, Colo. Great Plains Agric. Council seedlings. Tree Planters' Notes 19(1):7-9. Publ. 68. 458 p. 98. Scarborough, Betsy. 1979. Modifying container mediums 111. Toole, V. K., E. H. Toole, H. A. Borthwich, and A. G. to combat economic change. Am. Nurseryman Snow Jr. 1962. Responses of seeds of Pious taeda and 149(2):12-13, 123. Pinus strobus to light. Plant Physiol. 37:228-233. 99. Scarratt, J. B. 1982. Container stock specifications for 112. Ursic, S. J. 1961. Lethal root temperatures of 1-0 loblolly nothem Ontario. Pages 343-354 In Proc. Canadian pine seedlings. Tree Planters' Notes 47:25-28. 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