Propagation of Native Plants for Restoration Projects in the Southwestern U.S. - Preliminary Investigations 1
David R. Dreesen2 and John T. Harrington3
Abstract-Seed treatments to enhance germination capacity of a variety of native tree. shrub. forb. and grass species are reported. Scarification methods including hot water immersion (HW). mechanical scarification (MS). tumble scarification (TS), proximal end cuts (PEC), and sodium hypochlorite (SH) have been tested: Psorothamnus fremontii (HW. TS). Ceanothus integerrimus (HW). Ceanothus sanguineus (HW). Rhus g/abra (HW). Pte/ea trifoliata (PEG of seed separated by size and color). Rubus strigosus (SH), Oryzopsis hymenoides (TS), Co/eogyne ramosissima (TS). and a variety of native woody and herbaceous perennial legume species (HW. TS. MS). Gibberellic acid treatments were examined to overcome endo-dormancy of A/nus tenuifo/ia. A. ob/ongifolia, Rubus strigosus, and Oryzopsis hymenoides. Vegetative propagation methods investigated include mound layering of Platanus wrightii, root propagation of Populus tremu/oides. and pole plantings of riparian understory species (Amorpha fruticosa, Baccharis glutinosa, Forestiera neomexicana. and Chilopsis Iinearis).
INTRODUCTION pounded by the scarcity of propagu\es (seed or vegeta tive material) of some species or ecotypes. Restoration ofdisturbed lands in the southwestern U.S. has become a primary mission of many federal and Seed propagation ofnative species often requires state land management agencies and a regulatory growers to rely on information from closely related requirement for extractive industries. Frequently, horticultural species for seed treatment requirements. containerized or bare-root plant materials are used for While this information is useful, many species are reclamation activities following severe disturbance or produced by the horticulture industry because oftheir for introduction ofwoody plant species formerly present ease ofpropagation as well as other horticulturally on poorly managed lands. These plant demands have important traits. Secondly, seed used in the horticulture increased interest in propagation techniques and produc industry is often produced under optimum management tion methods for obscure native woody species. The conditions with seed lots having high percentages of lack ofpropagation information for many native species viable seed. In contrast, seed lots oflimited quantity and used in ecosystem restoration prompts nurseries to rely with unknown levels ofviability are most often encoun on experimentation to resolve propagation problems or tered by conservation nurseries. Therefore, two signifi forgo producing certain species. This problem is com cant factors must be addressed to develop seed propa
lDreesen, D. R. and Harrington, J. T. 1997. Propagation ofNative Plants for Restoration Projects in the Southwestern U.S. Preliminary Investigations. In: Landis, T.D.; Thompson, J.R., tech. coords. National Proceedings, Forest and Conservation Nursery Associations. Gen. Tech. Rep. PNW-GTR-419. Port/and, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station: 77-88.
2USDA-NRCS, Plant Materials Center, 1036 Miller Street, SW Las Lunas. NM 87031; Tel: 505/865-4684; Fax: 505/865-5163
3New Mexico State University, Mora Research Center, Mora, NM 87732 77 gation protocols for many native plants: first, seed seeD PROPAGATION refinement, or eliminating non-viable seed from the seed lot, and second, overcoming obstacles to germination of Scarification Studies recalcitrant species. These obstacles frequently fall Psorothamnus fremontii into two categories: impermeable seed coats This woody leguminous shrub found in the Mojavean and dormant seed. Typically, scarification and and Navajoan Deserts of the Colorado Plateau has stratification techniques are used to overcome these various pseudonyms including Dalea fremontii (Benson obstacles, respectively. and Darrow 1981 ). Common names applied to this species include Fremont dale a, indigo bush, and Johnson Seed refinement procedures for many tree and shrub dalea (Benson and Darrow 1981). The source of seed species are well known (Young and Young 1992, for this experiment was the Glen Canyon National Schopmeyer 1974a). Seed refinement involves increas Recreation Area in northeastern Arizona and southeast ing the percentage of viable seeds in a seed lot and is ern Utah. A means of improving total germination and often accomplished by seed sizing and liquid or air germination rate was essential because of limited seed separation techniques. However, seed refinement supplies. Previous trials with 2-year-old seed had shown techniques for many reclamation species have not been that traditional mechanical scarification (Forsburg J published or conventional techniques are not suitable seed scarifier) resulted in excessive seed breakage and due to seed properties. For example. seeds with integu was therefore not an acceptable scarification technique. ments or wings often preclude the use ofconventional gravity separation techniques. Seed was fractionated into large ( 11/64 to \3/64 inch (4.3 to 5.2 mm», medium (9/64 to 11/64 inch (3.6 to 4.3 Often. seed production of many species in native stands mm)), and small seed (7/64 to 9/64 inch (2.8 to 3.6 is sporadic with up to ten years intervening between mm» using round hole screens. Two scarification adequate seed crops. Vegetative propagation offers an treatments were evaluated. hot water soak and tumbling acceptable alternative propagation system to meet mechanical scarification. The hot water treatment production requirements. The horticulture industry is a involved immersing 5 to 109 of seed in 100 ml of90"C good source for vegetative propagation information of water and letting stand for I hour. After immersion, the species not historically produced in conservation nurser seed was separated into floating seed, swollen sinking ies. However, the differences between horticultural seed. and non-swollen sinking seed. The mechanical varieties and reclamation ecotypes are very pro scarification used a rock tumbler (one-liter capacity) nounced, largely due to adventitious rooting being with 100 g of pea-sized (10 - 15 mm) gravel. 75 g of strongly controlled by genetics. Cultivar releases in the coarse carborundum grit, and a rotation rate of 60 rpm. horticulture industry have often been attributed to the Two batches of medium-sized seed were subjected to I ability to produce adventitious roots. day and 3 days oftumbling. Seed receiving no scarifica tion treatment served as a control. Treated and control This paper will address some of our experience in the seed were planted in [288-cell square deep-plug] trays seed propagation of native tree, shrub, forb, and grass filled with Sunshine # I Mix®. Seeds were immediately species. These simple experiments are aimed at resolv planted and placed in the greenhouse (23°C day, 15"C ing problems with total germination percentage, rate of night). Germination was monitored weekly for the next germination (germination speed; days to total germina I 0 weeks. The study was replicated six times. tion ofa seed lot), and germination uniformity. Benefits associated with improving germination percent are Seed size influenced germination with larger seed straightforward. Improvements in germination speed having faster and greater germination (Figure I). The and uniformity can dramatically influence seedling tumbling mechanical scarification ofmedium-sized seed quality and production costs. In addition, several promis resulted in better germination than the control and hot ing vegetative propagation techniques are discussed. water treated seed and tumbling also significantly The paper is organized by the type oftreatment or improved germination speed. As the duration oftum propagation method being examined. Within each bling increased from one to three days germination section a summary report is provided on the species or speed was significantly increased; however only a group of species evaluated. 78 used to overcome obstacles associated with a hard, 50,------=--~~~------~ Days after SOWIng impermeable seed coat include hot water soaks, con c::::J 15 days ~ 46 days ~ 32 days _ 70 days centrated sulfuric acid, and mechanical scarification. 40 Variation between and within species to these treat ments makes prediction of treatment efficacy difficult. Also, scarification treatment methodology and severity may influence results.
Sulfuric acid treatments can be effective if the precise treatment time is known; excessive treatment duration 10 can destroy most or all of the seed. Insufficient dura tion fails to adequately break down the hard seed coat. o Difficulties in working with concentrated acid also Conli1.J1l HWIlrQ ConllMed HW_ ContISmI HWISmi TS-1_TS-_ dissuade some propagators from using this technique. Scarification Treatment I Seed Size Hot water soaks can be effective but research has s,..aSIz. ~.. shown that the germination response can be a function MId)o 9J64," <11184" Sni <~.. ofboth initial water temperature as weIl as the duration ofthe soak (Gosling et al. 1995). Ifthis interaction is not known for a particular species. excessive temperature Figure 1. Effect of seed size, hot water and tumble and/or duration can kill the seed. Some laboratory scarification treatments on the germination mechanical seed scarifiers can rapidly abrade seed (:I: standard error) of Psorothamnus fremont;;. coats through high-energy impact ofseed against an abrasive medium such as sandpaper. Again, excessive minor 4~;;) increase in total germination copmared with treatment time can destroy a batch of seed. Seed of the control was observed. Hot water scarification certain species are very easily damaged by these high treatments improved germination speed, while having energy impacts, such as some Lupinus species, whose only slight effects on total germination at the end of70 cotyledons are split apart by even the briefest conven days (Figure 1). tional scarifier treatment. In some species even when breakage is not observed, these impacts can kill the The effect of seed size was evident across the three embryo or damage other seed tissues. The need for seed conditions (swollen, non-swollen. floating) follow ing hot water incubation (Figure 2). Non-swoIlen seed 70 ______.__._.•.. had the greatest total germination at the end of the l2m..~ study (70 days) in all three seed sizes. Germination rate c::::J tS-D", IlIIIiIIlI -1M was fastest in the swollen seed in the two largest seed ~ 32-<111", s:ml ~Y' sizes, however, total germination was significantly less 50 " (at least 50%) relative to non-swollen seed. Only in the ~ c 40 largest seed size did floating seed have greater germina i tion rates than controls (Figure 2). .10 ! 30 Using seed sizing can be a viable means of seed 20 refinement in this species. Ifhot water scarification is 10 used, partitioning seed into swollen, non-swollen and floating fractions could be used to further improve o germination performance. S--Ull NS--t.rv F.t.rv s.Med Ns.Med F·Med S--Smi NS--Smi F·SmI Hot WSW Fractions Leguminous Species Figure 2. Germination (:I: standard error) of The water-impermeable seed coat of legume species swollen (S), not swollen (NS) and floating (F) generally requires scarification treatment to allow water Psorothamnus fremontii seed after hot imbibition and subsequent germination. Treatments often water treatment.
79 more reliable legume scarification infonnation for 1) control • no scarification treatment other use by propagators is substantial. Scarification than that received during standard seed infonnation would also benefit land restoration special cleaning procedures; ists who drill or hydroseed legumes and often desire 2) hot water· pouring hot water (90°C) over seed rapid gennination. batches and allowing to steep for 4 hours;
Many nurseries prefer to use hot water or mechanical 3) mechanical scarification· using a commercial small sample scarifier (ForsbergR) scarification to treat legume seed because the equip that employs a rapidly spinning paddle to throw ment for these treatments is available and because of seed against an abrasive lined drum (100 grit the potential hazard of using suI furic acid. A series of sand paper) for 3 to 75 seconds; experiments were conducted on several legumes examining hot water treatments and two types of 4) tumble scarification - using a rock tumbler with pea gravel and coarse carborundum grit for 2 to 3 mechanical scarification. The scarification treatments hours (see Psorothamnus section); evaluated were:
Table 1. Germination percentage of legume seed subjected to scarification treatments.
% Germination (Mean ± S. E.} Tumble Seeds per Mechanical Scarification Species Form Origin Replication Control Hot Water Scarification 2·3 Hrs
Amorpha eaneseens Woody Native 25 57 ± 7 48 ± 2 3*± 1 58 ± 5 Amorpha frutieosa (Cr Woody Native 100 25 ± 2 76*± 3 58*± 6 37*±6 Amorpha frutieosa (LL) Woody Native 100 21 ± 2 62*± 3 59*± 2 42*± 4 Caragana arboreseens Woody Exotic 100 34 ± 2 O*± 0 4*± 1 27 ± 3 Prosopis pubeseens (B) Woody Native 30 5±2 12*± 1 92*± 3 3±2 Prosopis pubeseens (BdA) Woody Native 30 5±3 23 ± 8 62*± 7 4 ± 1 Robinia fertilis Woody Native 30 31 ± 3 51 ± 7 17 ± 5 40 ± 6 Robinia neomexieana Woody Native 30 15 ± 4 39*± 4 78*± 2 17 ± 2 Astragalus lonehoearpus Herbaceous Native 20 8±3 2±2 52*± 2 2±2 Astragalus missouriensis Herbaceous Native 25 13 ± 2 13 ± 5 75*± 2 88*± 2 Oalea aurea Herbaceous Native 30 33 ± 3 65*± 5 10*± 0 70*± 3 Hedysarum borea/e Herbaceous Native 30 37 ± 4 52 ± 5 32 ± 5 39 ±4 Lathyrus eueosmus Herbaceous Native 30 2±2 O±O 38*± 5 2 ± 2 Lotus oroboides Herbaceous Native 35 3±0 30*± 1 77*± 11 7±4 Lupinus alpestris Herbaceous Native 30 27 ± 6 40 ± 8 41 ± 13 42 ± 2 Lupinus perennis Herbaceous Native 30 72 ± 6 57 ± 3 52*± 2 89 ± 4 Oxytropis lambertii Herbaceous Native 30 22 ± 9 16 ± 1 59*± 3 39 ± 4 Oxytropis serieeus Herbaceous Native 30 3±0 6±2 73 ± 2 9±2 Peta/ostemum eandidium Herbaceous Native 30 53 ± 4 46 ± 9 48 ± 1 55 ± 3 Peta/ostemum purpureum Herbaceous Native 30 67 ± 3 64 ± 9 63 ±4 63 ± 5 Thermopsis montanus Herbaceous Native 30 2±1 48*± 10 37*±7 3±2 Thermopsis rhombifolia Herbaceous Native 30 1 ± 1 14*± 4 42*± 8 2±2 Astragalus cieer Herbaceous Exotic 30 27 ± 2 51*± 2 62*± 5 36*± 1 Coronilla varia Herbaceous Exotic 30 29 ± 3 42*± 2 63*± 7 NO Lathyrus sylvestris Herbaceous Exotic 30 53 ± 5 58 ± 5 27'± 4 52 ± 3 Lotus eorniculatus Herbaceous ExotiC 30 78 ± 4 3*± 2 22'± 3 NO Medieago sativa Herbaceous Exotic 30 73 ± 2 75± 7 90*± 4 84*± 2
1C. LL. B. BdA refer to seed source locations. 'Percentages are significantly different from control (P<0.05). NO • No data available. 80 Treated and control seed were planted in [288-cell intensive investigation ofdifferent techniques on a square deep-plug] trays filled with Sunshine #1 Mix. variety of seed lots for each species. Seeds were planted immediately after treatment and placed in the greenhouse (23°C day, 15°C night). The Stratification Studies entire study was replicated three times. Alnus tenuifolia and Alnus oblongifolia Thinleaf alder, (Alnus tenuifolia), is a dominant shrub Treatment responses were species and seed source or small tree in riparian areas of the Rocky Mountains specific with no one treatment generating a consistent and Pacific Northwest. Arizona or New Mexican alder, effect (Table I). Mechanical scarification resulted in the (A. oblongifolia), is a riparian tree or shrub of the greatest gain in germination in woody legume seed lots mid-elevation drainages in the mountains ofsouthwest evaluated. Five ofeight seed lots had improved germi ern New Mexico and southeastern Arizona (Vines nation; however, the remaining three seed lots were 1960). Unlike A. glutinosa and A. rubra, little work has negatively impacted by mechanical scarification. been done on the propagation of these species. Fresh Tumble scarification improved gerrnination only in the seed of some Alnus species has been found to germi two ecotypes of Amorpha jrulicosa and did not nate without cold stratification; however, dried and detrimentally effect the germination of any other seed dormant seed of the same seed lot had improved lots evaluated. After these initial trials oftumble scarifi germination capacity following cold stratification cation, the need for longer treatment times became (Schopmeyer 1974b). The need for cold stratification apparent. Hot water scarification improved germination or prechilling can be variable among seed lots in half of the woody legume seed lots. Only in Amorpha within species of alder (e.g. A. rubra; Young and fi'llticosa was the gain in gerrnination comparable to the Young 1992). gain from the mechanical scarification. All scarification treatments were detrimental to gerrnination in Three experiments were conducted to examine the Carl/gana arhorescens. effect of gibberellic acid (GA) concentration and incubation length on the germination ofdried alder seed. Hot water and mechanical scarification treatments Seed used in the first experiment was from the Rio increased the germination of three herbaceous species, Costilla watershed in north-central New Mexico. LollIS oro/JOide.\·, Thernwpsis mOlltanus, and Thinleaf alder was the only species tested in the first Thermopsis rllOmhi/i)/ia by factors greater than ten. experiment. Seed of both thinleaf alder and Arizona Mechanical scarification was also highly effective on alder from the Gila National Forest in southern New Lathyrlls ellcosmus and Oxytropis sericeus. Astraga Mexico was used in the second and third experiments. lus deer and Coronilla varia benefitted from hot The first experiment examined the effect of GAJ water and mechanical scarification treatments. Only in concentration. Seven levels of GA) were evaluated: 0, four of the 19 herbaceous species was short duration 31,62, 125, 250, 500, and 1000 ppm. Seed batches of tumble scarification effecti ve in promoting germination. 100 seeds were placed into flasks containing 25 ml of In Dalea aurea, tumble scarification promoted total the GA solution and allowed to incubate for 44 hours. 3 • germination whereas mechanical scarification reduced Flasks were placed on a shaker table to provIde con total germination compared to controls. In three herba stant agitation. Following GAJ treatment, seed was ceous perennial species, Lupinus alpestr;s. rinsed with distilled water and sown into (288-cel1 Petalostemum purpureum, and Peta/ostemum square deep-plug] trays filled with Sunshine # I Mix and eandidium, none of the treatments were significantly placed in the greenhouse (21QC days and l3°C nights). different from the controls. Mechanical scarification The entire study was replicated three times. significantly reduced the germination of Dalea aurea, Lathyrlls sylvestr;s, Lotus eorniculatus, and Lupinus The second experiment differed in the seed sources perennis. Hot water treatment was detrimental to evaluated and the incubation technique. Specimen tubes Lotus corniculatus. (75 mt) were filled with 25 ml aliquots ofthe respective GA solutions and aerated using a porous aquarium J • The results above indicate the diversity of scarification stone connected with tubing to an aquanum pump. behavior exhibited by leguminous species. Refinement Following a 36 hour GA3 incubation, seed was handled of scarification procedures for legumes will require
81 sufficient to achieve maximum germination while at the ~~------24 c:::::: 17 Dayll AlIef Sowing shortest duration, 12 hours, germination continued to ~ 23 Day. After Sowing 22 _ 28 Day. After Sawing improve as concentration increased (Figure 6). ND No Data Available 20 18 While these results are preliminary, it would appear ~ 16 c .g 14 there are strong species and source differences in .~ 12 response to GA3 pretreatments in southwestern alders. ~ 10 At the highest concentrations evaluated, 500 and 1000 8 ppm GA), some seedlings became etiolated. Poor 5 overall germination capacity ofalder seed points to a need for seed refinement procedures. The winged "2 o .;-.::.;,0%;;,.:0:'::%:"'=.l... pericarp on alder seed reduces the efficacy ofdensity o 31 125 260 500 1000 separations using airflow seed separators. Preliminary Gibberellic Acid (~) Concentration (mgll} work with thinleaf alder seed indicates tumble scarification (see Psorothamnus section for details) Figure 3. Germination percentages (::t standard error) for effectively removes the wing which should allow Alnus tenuifolia seed soaked in gibberellic better seed refinement. We have yet to show whether acid (GA3) solutions of 0,31,62,125,250,500 this seed classification will result in increased and 1000 mg/l germination capacity. as described above. The entire study was replicated Rubus strigosus three times. The ability of wild raspberry (Rubus strigosus) to colonize disturbed sites and form thickets via root Incubation duration at lower concentrations ofGA3 was sprouts make it a likely candidate for disturbed land examined in the third experiment. Seed batches were revegetation efforts. Standard vegetative propagation incubated at 0, 125,250, or 500 ppm GA3 for 12,24, or procedures have been developed for production of 36 hours. The incubation apparatus and seeding method commercial raspberry cultivars and could be used to was as described in the second experiment. The entire produce cloned plant materials. However, to maintain study was replicated three times. some degree ofgenetic diversity and possibly reduce cost ofproduction, emphasis should be placed on seed Thinleaf alder seed from the Rio Costilla source re quired some level ofGA3incubation for germination. Both germination speed and total germination was 24 • enhanced by GA3 incubation (Figure 3). Germination speed increased with increasing GA) concentration, however total germination after 28 days was not improved by increasing concentration above 62 ppm --+-- Ainu!! tenudOi,a (Gila) • GAj Both alder species from the Gila National Forest -:!-- Ainus oblongdoliB (Gila) were able to germinate with no GA) treatment and only in thin leaf alder did GA3 incubation improve germination after 28 days (Figure 4). Improvement in germination was slight going from 15% for control seed to 21 % for the three highest GA3 concentrations. The effect of GAl incubation duration and concentration was differ ent for the two species. In Arizona alder, response to Gibberellic Acid (G~ Concentration (mgll) GA3 was variable across concentration and duration, especially in the two intermediate concentrations of Figure 4. Germination (::t standard error) after 28 GAl' 125 and 250 ppm (Figure 5). In thinleaf alder all days for Alnus tenuifolia and A. oblongifolia treatments improved germination relative to controls. At following 36 hour gibberelliC acid the longest duration, 36 hours, 125 ppm GA3 was (GAl) incubation. 82 18 __ 12-Hour ImmenIIOIl -0 24-Hour ImrnerllOn Bleach treatments between 4 and 48 hours duration 18 ...... 38-Hour ImmetSIOn showed 2 to 3 times greater germination than the
1.. control and 96 hour treatments (Figure 7). Translucent ...... seed coats were observed in a few seed in the 24-hour / ...... bleach incubation, for many seed in the 48-hour bleach --"""'"'...... ~ ...... incubation, and for all seed in the 96-hour incubation. ? The 96 hour bleach incubation resulted in slightly less F""':':-'--~ than 10% ofthe seed beginning to disintegrate. Addition ofa gibberellic acid incubation improved germination of 6 - { both the 48 and 96 hour bleach treatments. On the basis of this limited study with one seed source, a 48 hour, o 100 200 300 400 500 600 I % sodium bleach treatment followed by a 72 hour, 250 ppm GA} incubation yielded the greatest improvement in germination percentage (73% versus the control at 17%). ) Figure 5. Influence of gibberellic acid (GA3 soak concentration and duration on the germination (± standard error) of Arizona Coleogyne ramosissima Alder(Alnus oblongifloia) Blackbrush (Coleogyne ramosissima) is a dominant shrub in many plant communities occurring in the propagation. Treatment with a bleach solution ( 1% transition between Mojavean and Sagebrush Deserts sodium hypochlorite) has been reported to enhance (Benson and Darrow 1981). Published literature indi Rubus germination (Brinkmann 1974b, Rose et aL cates a prechilling (i.e., cold stratification) treatment is (996). To examine the suitability ofthis technique on required for Coleogyne (Young and Young 1992). Rubus strigosus, fruits were collected from the In initial trials, seed harvested from Glen Canyon Molycorp mine site in north-central New Mexico in National Recreation Area had 56% germination with no early October and immediately depulped by fermenta seed treatment but 83% with 7 weeks of cold stratifica tion for 2 weeks. Seed was then air dried and classified tion. A second study was conducted to examine other by density using an airflow seed separator. Only the seed treatments in combination with cold stratification. heaviest seed, (average seed mass of 1.8 mg), was Seed used in this study was 5-year-old seed from used in this experiment. Five durations (4,8,24,48,96 Canyonlands National Park. Four seed treatments were hours), ofsoaking in I % bleach solution were evaluated along with a control consisting ofa 48 hour soak in distilled water. In addition, four bleach/GA} treatments ~~------22 were used. These treatments consisted of: water soak 20 (control), then 250 mg/l GA} for 72 hours; 48 hour 18 bleach incubation followed by a 72 hour, 250 ppm GA} ~ 16 incubation; 48 hour bleach incubation followed by a 72 I 14 hour, 1000 ppm GA} incubation; and, 96 hour bleach ~ 12 incubation followed by a 24 hour, 1000 ppm GA}
83 80 SodNm Hypoc:tllome f 1%l Treatment Ourattml stratification ofblack brush. ()'Hr~t""H.r 4-fit =-:: .:lJ,.Hr 70 &-Hr _ 9&-Hr
NO~NoO_A""" Combination of Scarification/Stratification 60. Oryzopsis hymenoides Indian ricegrass (Oryzopsis hymenoides) is an impor tant reclamation grass on disturbed lands with sandy or rocky soils in the west and is being used increasingly as a xeriscape ornamental. Previous work has shown this species has recalcitrant seed. Studies by Khan ( 1997) r. indicate both seed coat and embryo dormancy exist in ! this species. Based on positive responses to tumble scarification and GA, treatments with other species, Control GA3 250 mgII GA 31000 mgll J these methods were applied to attempt to enhance the Seed Treatment germination of O. hymenoides >Nezpar'.
Figure 7. Effect of sodium hypochlorite (1 %) treatment Seed used in this experiment was from a commercial duration and subsequent gibberellic acid (GAl) source. A factorial combination oftumble scarification immersion on the germination (± standard error) of Rubus strigosus of0, 2, 5, and 7-days and GA j incubations (0 or lOOn ppm for 24 hours) were examined. Following treatment, seed batches were rinsed thoroughly and sown into [288-cell square deep-plug] trays containing Sunshine examined. These treatments included a 24-hour soak in # I Mix. Trays were then placed into the greenhouse 250 ppm GA , a 24-hour soak in de-ionized water, a 24 3 (23"C day and 13"C night) and monitored for 2g days. hour tumble scarification (see Psorothamnus section for The study was replicated 5 times. details), and a untreated control. All treated seed was rinsed thoroughly with distilled water. All treatments Total germination improved with increasing duration of were then subdivided into groups receiving seven weeks tumble scarification (Figure 9). This response was more ofcold stratification and groups receiving no cold pronounced in the GA, treated seed. These results stratification. Seed was sown in [288-cell deep-plug] indicate increasing the duration oftumble scarification trays containing Sunshine # 1 Mix. Trays with seed causes a rcduction in seed coat donnancy. Gibberellic receiving cold stratification were placed in plastic bags acid treatment appears to overcome embryo dormancy with aeration holes and placed in walk-in coolers (4"C); after seven weeks, they were removed from the cooler, 60------············-----· taken out ofthe bags and placed in the greenhouse (21 84 l 7~------~c::::J 24-1tt __ triangular cross section. The seed was also classified as IZ:ZlI 24-H, GA, (1000 mg.I)1 to color: light green throughout (Green), some light 6 green sections along with tan or brown (Mix), and tan or brown throughout (Brown)_ This classification 5 generated six seed categories as there were no seed in the large brown, small green or triangular mixed catego ries. To improve gennination, the proximal end (i.e., attachment end) was cut using a scalpel until the void in the seed cavity was exposed. This proximal end cut 2 was perfonned on hal f of the seeds in each seed lot. Treated and untreated (control) seed was sown into 288-cell flats containing Sunshine # I mix and cold o -\---.....1-----l, Control 2-0ay 5-Day stratified for 18 weeks at 4°C. This experiment was Tumble scarification Period only conducted once. Cutting the proximal end resulted in increased gennina Figure 9. Effect of tumble scarification and subsequent immersion in gibberellic acid (GA3) on tion for all but the triangular brown seed class. Un the germination (:t standard error) of treated seed in the triangular brown class had the Oryzopsis hymenoides. highest gennination rate (16%) of all the control seed classifications and was comparable to the gennination (endo-donnancy) . rate of all but the large green and triangular green treated seed classes (Figure 10). The greatest gennina Rhus spp. and CCal10tlllls spp. tion observed was for the treated large grecn seed Seed lots (2 to 3 g), from commercial sources, of which had 50% gennination. Ceanotlllls integerrimlls. C. sangllincus, and Rhus glahra were immersed in 90"C water or 25"C water The results indicate the potential for screening seed for 22 hours_ Treated seed were sown in [288-cell based on color, size and shapc_ The recommended square deep-plug] trays with Sunshine # I Mix and cold proccdure based on these results would be using large stratified for 12 weeks. Following cold stratification green seed and cutting the proximal end prior to an 18 treatment the trays were placed into a greenhouse week cold stratification treatment. (23"C day, 15°C night). Germination was monitored for 24 days. Seed treated with the hot water had elevated 60 gennination relative to the seed soaked in room tem c:= Cut End perature water. Gennination of hot water incubated ~ Intact seed versus the seed incubated at room temperature 50 was: C. integerrimus, (73% vs. 3%) C. sanguineus, 40· (66% vs. 7%) and Rhus glahra (29% vs_ 1%). This ~ i enhanced gennination by hot water treatments prior to i I 30 ~, cold stratification has been reported in these genera .Ii ..E previously (Brinkman I 974a, Reed 1974). (!) 20 J Ptelea trifoliata 10 Common hop-tree (Ptelea trifoliata) is widely distrib 0% uted with many varieties or subspecies found throughout 0 the U.S. (Vines 1960). Seed used in this experiment Large Large SmaD Small Triangular Triangular Green Mixed Mixed Brown Green Brown was collected in 1992 and 1994 from the Cibola Na Seed Size (Shape) and Color tional Forest in canyon bottoms within the ponderosa pine zone. After rubbing to remove the winged pericarp, Figure 10. The influence of proximal end cut and seed the seed was separated into 3 morphological classes: size, shape. and color on the germination of small «13 mm length), large (>13 mm length), and Pte/ea trifoliata. 85 Vegetative Propagation the stems and filled with medium. No attempt was Mound Layering of Platanus wrightii made to remove any leaves from the stems before Arizona sycamore (Platanus wrightii) is an important filling the container. Mounds were fertilized during June component of riparian ecosystems at mid-elevations in with 50 (small mounds) to 100 grams (large mounds) of southwestern New Mexico and southeastern Arizona. 17-6-12 controlled release fertilizer (SierraR 3-4 month As riparian restoration projects in these areas become plus minors). more common, the demand for large containerized materials will likely expand. Although Arizona sycamore A Roberts Mini-flow Spot-SpitterR was inserted into the can be grown from seed, a more rapid production top of the mounded medium to wet most ofthe mound method for larger plant material is desirable. In addition, surface (large stock plants required several Spot vegetative propagation could be used to preserve Spitters). Mounds were irrigated daily during the clones with desirable traits and when viable seed is growing season. Mounds were irrigated every 2 weeks not available. in the winter ifno precipitation had occurred. During winter months, all side shoots were pruned to ease Mound layering techniques are sometimes used to harvest and reduce the potential leaf area of the produce rooted cuttings of species not easily amenable propagule. Stems were in the mound layering system to more traditional cutting propagation methods. for a total of9 to 10 months. In early spring (March), Through trial and error, a methodology has been devel mounds were disassembled by removing the bottomless oped to produce large rooted whips of Arizona container and as much medium as possible by hand. sycamore that could be used for production of Stems were severed 2 to 5 cm above the soil surface large containerized stock or possibly as bare root with loppers or pruning saw. Large stems were planted planting material. into 5-gallon containers coated with copper hydroxide paint (SpinOutR) and small stems « 1.5 cm) into onc To develop stock plants, seedlings ofa Gila River gallon tree pots. ecotype in I-gallon tree pots were planted in 1993 into sandy loam soil. Stock plants were heavily fertilized in Average number of large stems (caliper> 1.5 em) May of each year. Surface soil was amended with produced by 3 year old stock plants was 4 per plant in sulfur on an annual basis to prevent chlorosis; alkalinity 1997. Several stock plants produced more than 10 largc of irrigation water was approximately 150 mg/L as stems while others produced only one. Out of73 large stems produced, 34% exhibited good to excellent CaCOJ with a pH of8.0. During establishment, the stock plants were flood irrigated on a weekly basis rooting, 27% had poor to fair root development, and during the growing season. 39% were etiolated with few or no fine roots. Dormant stems layered during the previous year were Large stem transplants with some root development had harvested just above the soil surface (2 to 5 cm) in early 100% survival when evaluated three months after spring (March). Any residual media from the previous transplanting. Etiolated large stems had 73% survival. years mound was removed to allow new stems to easily Vigor ofthe large transplants (both rooted and etiolated) emerge from the crown of the stock plants. By late 3 months after transplanting was as follows: 74% with May, new stems were approximately 0.5 meter high good to excellent vigor, 18% with poor to fair vigor, and the mounding process was initiated. One ofthree and 8% dead. soilless media were used: a pumice, peat, and bark mix; a commercial peat and perlite mix; or, pumice alone. To Transplanted stems exhibited slow growth until the root reduce cost, a technique to minimize the amount of system was well developed. Spring application of sulfur media required for mounding was employed. Inverted and controlled release fertilizer were used. Each 5 bottomless nursery containers were used to contain the gallon container was placed in a pot-in-pot system with mound. For smaller stock plants (fewer than 5 stems), a copper-coated fabric (Tex-R7InsertR) between the two bottomless 5-gallon egg can was used; whereas, for pots to limit roots from growing through the bottom pot large stock plants (from 5 to 15 stems) a container into the soil. A Spot-Spitter inserted into each pot equivalent to a bottomless squat 20-gallon nursery can provided daily micro-irrigation ofthe newly transplanted was used. The bottomless container was placed over stems; after the root system was well developed, the 86 1 large leaf area necessitated daily watering. The 5-gaUon (Baccharis glutinosa), one ecotype of desert willow, I transplants were ready for field planting approximately and one ecotype of false indigo bush. Little success was \ 10 months after potting. achieved with cuttings ofthree leaf sumac, Arizona sycamore, and one ecotype of desert willow and false Some preliminary work has been done with mound indigo bush. layering of other riparian woody species. Positive results have been obtained with Arizona alder, desert Limited plantings with these species have been per willow (Chi/opsis linearis), false indigo bush, and three formed in riparian areas to date. Preliminary results are leaf sumac (Rhus trilobata). Stock plants of Arizona promising for New Mexico olive, seepwillow, and false alder, thin leaf alder, and water birch (Betula indigo bush. More extensive field-testing is required to occidentalis) are presently being grown to test mound validate these results and examine variability among layering of these species. ecotypes within species. Novel Species for Understory Pole Plantings Propagation of Populus tremuloides Successful establishment of cottonwoods (Populus from Root Cuttings spp.) and willows (Salix spp.) using pole plantings is Vegetative propagation of quaking aspen (Populus becoming an accepted restoration technique for dis tremuloides) using root cuttings is a traditional horticul turbed riparian areas. This success has engendered tural practice. More recent developments have used interest in determining whether other woody riparian root cuttings to produce suckers, which are rooted as species could be planted as dormant pole cuttings. Use conventional softwood stem cuttings (Schier 1978). Our oflong dormant cuttings (i.e., whips and poles) allows objective was to determine the efficacy ofdirect planting in deep holes reaching into the capillary fringe sticking root cuttings into 164 ml containers (Super Cell above the water table. Numerous successful pole Cone-tainer). Cutting length and diameter were re plantings have resulted in many land managers adopting corded before planting in order to relate root cutting this technique for riparian restoration where the lack of dimensions and volume with survival and vigor ofthe persistent near surface soil moisture would limit survival resulting plant. Aspen stock plants were grown in 5 ofcontainerized stock or seeded materials. gallon containers using a pot-in-pot system. The stock plants were derived from 6 clones growing on the Studies were required to determine whether other Molycorp mine site (Questa, NM). Root cuttings were woody riparian shrub and tree species were amenable taken from the periphery ofthe root ball in March. to pole planting technology. These investigations were Average number of cuttings produced per stock plant started in 1994 by evaluating the survival ofdormant was 9 large (> 6 mm diameter), 8 medium (4 to 6 mm), hardwood cuttings planted into a flood irrigated agricul and 8 small (2 to 4 mm). Cutting diameter ranged from tural field situation. A cutting's ability to survive and 2 to 13 mm and length ranged from 3 to 14 cm. Cuttings grow should be a good indicator of successful establish were immersed in a Captan suspension and stored at ment by pole planting in riparian areas. Appreciable 4°C in damp peat moss until May when the cuttings survival and growth was obtained with cuttings ofNew were planted in a Sunshine # 1 - perl ite mix (2: 1). Mexico olive (Forestiera neomexicana), seepwillow Cuttings were inserted vertically with proper polarity into dibbled holes until the top ofthe cutting was just Table 2. Survival and vigor class percentages of below the media surface. Populus tremu/oides propagated by root cuttings. Rooting success after eight weeks ranged from 42% to Percentage in Vigor Class 91% (Table 2). In most instances, clones with higher Clone Excellent Good Fair Poor Percentage Alive rooting percentages had higher proportions ofmore 1 23 14 10 9 56 vigorous plants. Data relating cutting size attributes to 3 19 21 21 17 78 rooting and subsequent vigor have not been analyzed 4 51 19 9 12 91 5 11 15 5 11 42 yet. These relationships will indicate the size ofthe 6 42 25 6 5 78 smallest cutting which can be used and still obtain 7 26 20 7 19 72 acceptable survival percentages and vigor. 87 IMPLICATIONS Brinkman. K.A. 1974b. Ruhus L., blackberry, raspberry. In As forestation projects continue to change from tradi Seeds of Woody Plants in the United States. Agriculture tional reforestation to remediation ofdisturbed lands, Handbook No. 450, Forest Service, U.S. Dept. OfAgric. p. nurseries will need to develop strategies for producing 738-743. these difficult to propagate species. These studies and Gosling,P.G., Y.K.SamueJ,andS.K.Jones J995.A others indicate the need for more work to be done on systematic examination ofgermination temperature, the propagation of many ofthese plants. Emphasis will chipping and water temperature/soak duration pretreat need to be placed on ecotypical variation, seed refine ments on the seeds of Lellcaena leucocephala. Seed Sci. ment, and the exploration of new seed and vegetative & Technol.23: 521-532. propagation techniques. The nature and size of these new planting (forestation) efforts will likely preclude the Khan. A.A. 1997. Quanti fication of seed dormancy: physi intensive efforts and expenditures which have optimized ological and molecular considerations. HortScience 32(4): production oftraditional timber species such as ponde 609-614. rosa pine, loblolly pine or douglas-fir. Rather the species Reed. M.l. 1974. Ceanofhus L. Ceanofhus In Seeds of required for restoration will be site specific and used in Woody Plants in the United States. Agricultural relatively small areas. Handbook No. 450, Forest Service, U.S. Dept. ofAgric. p.284-290. Rose, R.. C.E. Chachulski, and D.L. Haase. 1996. Propagation ACKNOWLEDGMENTS ofPaci fic Northwest native plants: a manual. Volume One. Nursery Technology Cooperative, Oregon State The studies reported above were made possible by University, Corvallis, OR. 66p. funding support from the following organizations: Molycorp Inc. (Questa, NM), National Park Service, Schier. G.A. 1978. Vegetative propagation ofRocky Gila National Forest, Apache-Sitgreaves National Mountain aspen. USDA Forest Service, General Technical Forest, Cibola National Forest, Carson National Forest, Report INT-44. August 1978. 13p.lntermountain Forest Army Corp of Engineers, Bureau of Reclamation. and Range Experiment Station, Ogden. Utah g440 I. Bureau of land Management, U.S. Fish and Wildlife Schopmeyer, C.S. 1974a. Seeds of Woody Plants in the Service, New Mexico State University, and Natural United States. Agricultural Handbook No. 450. Forest Resources Conservation Service. Service, U.S. Dept. ofAgric. 883pp. Schopmeyer. C.S. 1974b. AIII liS B. Ehrh. Alder. In Seeds of Woody Plants in the United States. Agricultural LITERATURE CITED Handbook No. 450, Forest Service, U.S. Dept. ofAgric. p.206-211. Benson, L., and R. A. Darrow. 1981. Trees and shrubs ofthe southwestern deserts. University of Arizona Press, Vines, R.A. 1960. Trees, shrubs, and woody vines of the Tucson. 416 p. southwest. University of Texas Press, Austin and London. 1104 p. Brinkman. K.A. 1974a. Rhus L. Sumac. In Seeds ofWoody Plants in the United States. Agricultural Handbook No. Young, l.A. and C.G. Young. 1992. Seeds of Woody Plants in 450, Forest Service, U.S. Dept. ofAgric. p. 715-719. North America. Dioscoriodes Press, Portland, OR. 407 p. 88 National Proceedings: Forest and Conservation Nursery Associations 1997 Thomas D. Landis and Jan R. Thompson, Technical Coordinators u.s. Department of Agriculture Forest Service Pacific Northwest Research Station Portland,OR97208 of General Technical Report PNW-GTR-419 December 1997 This publication was published as a cooperative effort by the Pacific Northwest Research Station and the Pacific Northwest Region.