Propagation of Stewartia: Past Research the Propagation Problem

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propagation techniques to overcome Propagation of Stewartia: Past Research the propagation problem. Various as- Endeavors and Current Status pects of propagation such as seed scarification, cutting type, rooting hormone, rooting medium, nutrition, Ajay Nair1,2 and Donglin Zhang cold acclimation, and micropropagation have been specifically targeted and show promising results. Stewartia ADDITIONAL INDEX WORDS. rooting, overwintering, KIBA, stratification, semi-hardwood has been a plant of interest not only to the propagation experts, but also to SUMMARY. Stewartias (Stewartia spp.) are prized for their camellia (Camellia taxonomists and molecular biologists. japonica)-like flowers, intense fall color, and exfoliating bark. In spite of having Researchers have conducted genetic outstanding ornamental value and features, these plants are not readily available for linkage studies to track their center of landscaping in the horticulture trade. The primary reason stated is the difficulty of origin and also to establish relation- its mass propagation and production. In the last two decades, considerable research has been conducted on various aspects of stewartia propagation such as seed ship between native and introduced germination, cutting type, light, rooting medium, rooting hormone, cold species. With close to a dozen species acclimation, and tissue culture. In this article, we discuss factors that directly and cultivars in different hardiness influence propagation of stewartia and we highlight results of published studies to zones and appealing morphological propagate stewartia. The evidence indicates success in adventitious rooting of characteristics, stewartia certainly has cuttings but at the same time recognizes the continuing challenge associated with a remarkable potential of being a front overwinter survival. Sexual propagation has also been studied, but its commercial yard ornamental tree. This article application is limited. To date, there is lack of concrete information on why summarizes past research endeavors stewartia remains under-represented in our landscapes. It still remains unclear if it is undertaken to propagate stewartias the lack of consumer demand or existing propagation difficulties that is the cause of and also focuses on techniques and under utilization of stewartia. Given the information from most published studies, we suggest further research on the aspect of overwinter survival in addition to approaches to increase commercial a survey of the nursery and greenhouse industry to accurately determine the cause availability. behind the absence of stewartia in horticultural trade. Seed propagation One of the fundamental prob- here has been constant de- white camellia-like flowers and lems associated with sexual (seed) mand in the horticulture trade smooth mottled bark (Hohn, 1994). propagation in stewartia is that it is Tto produce plants that have The bark flakes in patches to reveal a slow and unreliable process mainly unique features such as short stature, buff, tan, cinnamon, and plum colors because of complex dormancy mech- prolific summer growth, intense fall during winter (DeWolf, 1969). With anisms in the seed (Curtis et al., color, winterhardiness, etc. Stewartia, their beautiful and appealing flowers, 1996). Irregular and infrequent seed- with its remarkable traits and features, magnificent exfoliating bark, spectac- ing habit, low seed viability, and short qualifies to be in that category. Stew- ular fall colors, and low insect and longevity impede large-scale nursery artia comprises of eight to 21 species, disease problems, stewartias are an all production. Seeds of stewartia require depending upon the author (Li, season high-demand landscape tree certain warm and cold stratification 1996; Yang, 1997). Stewartias are (Spongberg and Fordham, 1975). treatments to germinate successfully. distributed on both sides of the In spite of having such outstand- The standard nursery practice for pro- globe, mostly dwelling in the wood- ing ornamental values and features, duction of stewartia seedlings is to lands. Stewartia comprise both tem- stewartia is not readily available for sow seeds outdoors in the fall and to perate (deciduous) and tropical landscaping in the horticultural trade. allow 2 years for seedling emergence. species (evergreen). One of the most The primary reason stated is the lack Under normal conditions, seeds that important stewartia species in the of efficient propagation techniques fall on the ground germinate not the trade is japanese stewartia (Stewartia and the propagation challenges asso- following spring, but the one after pseudocamellia), which was introduced ciated with stewartias (Struve and (Hohn, 1994). To resolve this dor- into the United States in 1866 by Lagrimini, 1999). Much work has mancy problem, experiments have Thomas Hogg, Jr. to a private green- been conducted to overcome propa- been conducted on mechanical and house in New York (DeWolf, 1969). gation difficulties and to develop spe- chemical seed treatments to break Stewartia grows well in U.S. Depart- cific techniques, but the commercial seed dormancy and enhance germina- ment of Agriculture hardiness zones availability of stewartia is still low. tion percentages. Oleksak and Struve 5 to 8 (Dirr, 1998). Most of the ste- Researchers have, to a large extent, (1999) demonstrated that seed ger- wartias are small trees reaching 30 to focused on various sexual and asexual mination of japanese stewartia is 40 ft in height and are easily distin- guishable by their numerous creamy Units Department of Plant, Soil, and Environmental Sci- To convert U.S. to SI, To convert SI to U.S., ences, University of Maine, Orono, ME 04469 multiply by U.S. unit SI unit multiply by 1Current address: Department of Horticulture, Michigan 0.3048 ft m 3.2808 State University, East Lansing, MI 48824 1 ppm mgÁL–1 1 2Corresponding author. E-mail: [email protected]. (F – 32) O 1.8 F C(1.8·C) + 32

• April 2010 20(2) 277 REVIEWS promoted by desiccation avoidance, 1982)], azalea [Rhododendron spp. carbohydrate storage, cold acclima- gibberellic acid (GA3) treatment, and (Smalley and Dirr, 1986)], and japa- tion, and overwinter storage temper- warm and cold stratification. If the nese stewartia (Wilson and Struve, ature. The following sections will look seeds are exposed to ambient room 2004). Stem cuttings of stewartia into each of these aspects individually. temperatures for 48 h or 80 C drying typically root well and develop healthy conditions for 24 h, they lose viability root systems in their first season, but Type and characteristic completely (Oleksak and Struve, 1999). are prone to die during the following of cutting The study also indicated that expos- winter or shortly after the onset of The type of cutting chosen for ing seeds to a 24-h aerated water soak growth the following spring (Dirr and propagation significantly affects root- in 1 mM GA3 and 3 months warm Heuser, 1987; Wilson and Struve, ing and subsequent overwintering of stratification (25 C) followed by 7 2004). The symptoms associated with cuttings (Hartmann et al., 2002). Soft- months cold stratification (4 C) sig- overwinter mortality are diverse. Cut- wood cuttings ensure higher chances of nificantly increased seed germination. tings put forth frail new growth that obtaining post-rooting growth, which Final germination was 70% when withers off and, ultimately, the cut- will increase the production of photo- seeds were given a 3-d aerated water tings die off (Waxman, 1965). In synthates (Smalley et al., 1987). How- soak in 1 mM GA3 followed by 3 months some cases, rooted cuttings fail to ever, softwood is not always the warm, moist stratification (25 C) and 4 break bud after winter dormancy preferred source of propagation, as months cold stratification (7 C) (Struve (Curtis et al., 1996). softwood cuttings tend to wilt easily et al., 1999). Germination in this case Even though some success has and need special care and attention was not synchronous. Depending on been reported (Perkins and Bassuk, (Hartmann et al., 2002). the source of the mother plant, germi- 1995), the overwinter survival prob- Rooting ability and overwinter nation varied from 30% to 90% for seeds lem of stewartia has been largely un- survival is influenced by the type of givena3-daerated1mM GA3 soak resolved. To avoid this overwintering cutting in many genera such as camel- followed by alternating warm stratifica- problem in tall stewartia (Stewartia lia (Macdonald, 1974), sugar maple tion temperature (20/12 Conan monadelpha), Dirr and Heuser (1987) (Donnelly and Yawney, 1972), witch- alternating 12-h cycle for 3 months) suggested layering as an alternative hazel [Hamamelis spp. (Dirr and before cold stratification for 10 method. Hohn (1994) cited the pos- Richards, 1989)], and oak [Quercus months. Cold stratification alone for sibility of grafting in stewartia, using spp. (Drew et al., 1993)]. For moun- 9 months, without prior warm strat- tall stewartia and japanese stewartia as tain camellia, cuttings taken early in ification, resulted in poor germina- understocks. He further suggested the season (softwood cuttings) are tion percentages (less than 1%). The that mountain camellia (Stewartia an excellent source of propagation optimum temperature for warm ovata) and chinese stewartia (Stewar- (Curtis et al., 1996). Softwood and moist stratification was 15 C. tia rostrata) can be successfully lay- semihardwood stem cuttings of stew- Although success has been ered, but layering cannot become artia rooted when treated with 3000 to reported in breaking and overcoming a commercial propagation protocol 8000 mgÁL–1 auxin solutions (Ekstrom dormancy of the seed (Oleksak and due to the limitation of low number and Ekstrom, 1988; Halward, 1966). Struve, 1999; Struve et al., 1999), of plants that could be produced. Flemer (1982) listed the korean form this technique has not been adopted Gouveia (1991) reported 80% of japanese stewartia as a species that by the industry. A drawback of seed rooting in propagating korean stew- could be successfully propagated from propagation is that propagation of artia, treating three noded cuttings softwood cuttings. Late June to early a specific cultivar is impossible when taken between mid-June to mid-July July is the recommended period to propagated by seeds. Asexual propa- with 2000 mgÁL–1 indolebutyric acid collect stewartia cuttings for maximum gation is by far the most common and (IBA). However, there was no infor- rooting (Fordham, 1982). Gouveia widely adopted method to propagate mation provided in the article regard- (1991) reported that cuttings of and maintain genetic integrity of or- ing the percentage of cuttings that korean stewartia (Stewartia koreana) namental plants in the nursery trade. were successfully overwintered. Struve taken in mid-June exhibit good root- and Lagrimini (1999) propagated ing and establishment. Results from Asexual propagation japanese stewartia and overwintered the study conducted in our laboratory Asexual propagation by soft- them in large quantities. Unfortu- have demonstrated that semihardwood and semihardwood cuttings is nately, once the cuttings were moved wood cuttings of japanese stewartia, the most common technique in the to outdoor conditions, only 17% of taken in July and treated with a combi- nursery industry. However, successful rooted cuttings survived. In the case nation of rooting hormones, produced cutting propagation of many woody of seedlings, the survival was reported satisfactory rooting percentages (Nair plant taxa is limited by poor over- to be 48% (Struve and Lagrimini, et al., 2008). winter survival in the first propagation 1999). Therefore, overwintering is The source plant and the juve- year (Smalley and Dirr, 1986). Low an important aspect for successful nility aspect of the cuttings is also an overwinter survival has been a signifi- propagation of stewartia and other important factor to consider in cut- cant problem in several important woody plants. There are a number of ting propagation. In terms of juvenil- plants such as sugar maple [Acer factors that are directly associated with ity, the position of the cutting on the saccharum (Donnelly and Yawney, overwintering of cuttings including: source significantly affects the sub- 1972; Goodman and Stimart, 1987)], type and characteristic of cutting, sequent rooting and overwinter sur- birch [Betula spp. (Flemer, 1982)], wounding, rooting hormone, root- vival. Ideally, cuttings should be witchalder [Fothergilla spp. (Fordham, ing medium, nitrogen fertilization, taken from juvenile wood. In the case

278 • April 2010 20(2) of japanese stewartia, it was demon- auxins should be carried out with KIBA (quick dip) + 3000 mgÁL–1 strated that rooting and survival rates caution, as supraoptimal concentra- IBA (powder) in japanese stewartia. were high for cuttings taken from the tions could reduce overwintering. In The percentage of rooted cuttings was basal wound shoots when compared many rooted cuttings, higher auxin significantly lower for control treat- with canopy cuttings (Haynes, 1999). concentrations used for rooting set ment compared with hormone treat- Attempts made in our laboratory to a period of dormancy before they ments. There were no differences propagate japanese stewartia from were able to resume shoot growth among hormone treatments. How- hardwood cuttings were unsuccessful (Goodman and Stimart, 1987). Sun ever, there were significant differences (Nair, 2006). and Bassuk (1993) reported that IBA in the overwinter survival rate among increased adventitious root formation treatments, with the combination Wounding and rooting but also inhibited budbreak in single treatment exhibiting highest overwin- hormone node ‘Royalty’ rose (Rosa ·hybrida) ter survival rate (64.2%). Thus, it Root production in stem cut- cuttings. Because early budbreak and seems that the rooting hormone con- tings can be substantially increased shoot growth are considered impor- centration and the rooting hormone by wounding the base of a cutting tant for better overwinter survival, formulation play an important role in (Hartmann et al., 2002). Wounding high concentrations of auxin could overwinter survival. increased root production in rho- be detrimental (Sun and Bassuk, dodendron, juniper (Juniperus spp.), 1993). Rooting medium and maple (Acer spp.), and arborvitae Forstewartia,variableauxincon- fertilization (Thuja spp.) (Wells, 1962). Wound- centrations have been reported to be The propagation medium ing is not only considered to speed up successful. Fordham (1982) propa- should hold the cutting in place, pro- the rooting process, but also to im- gated a majority of stewartia species vide adequate moisture, be free of prove the quality of roots produced successfully using 0.8% (8000 mgÁL–1) pathogens, permit exchange of air at (Hartmann et al., 2002). Curtis et al. formulation of IBA in talc, with the the base of the cutting, and create (1996) stripped the lower leaves of fungicide thiram added. He also a dark or opaque environment. Better mountain camellia, which enhanced reported a high percentage of rooting, rooting is often associated with in- auxin uptake and increased rooting employing a quick dip treatment using creased porosity (Gislerod, 1983). In percentage. Gouveia (1991), however, a combination of IBA plus NAA at stewartia, a medium composition, found wounding to be unnecessary in a2500mgÁL–1 concentration. Haynes perlite + Perennial Mix (Scotts-Sierra, korean stewartia. Wounding sites can (1999) reported high rooting percent- Marysville, OH), which provided op- also serve as an easy entry point for ages, up to 100%, in semihardwood timal aeration, ensured higher root- pathogens and other harmful microor- cuttings of japanese stewartia when ing, minimal rotting, and a better ganisms. To overcome this problem, treated with 10,000 mgÁL–1 potassium overwinter survival (Nair et al., Dirr and Heuser (1987) suggested salt of IBA (KIBA) solution as quick 2008). It has been demonstrated that a fungicide treatment for propagation dip. On the contrary, Struve and stewartia can be rooted in a wide range of stewartia. Spongberg and Fordham Lagrimini (1999) promoted lowering of rooting medium. Researchers have (1975) added 15% of fungicide thiram auxin concentrations for rooting of experimented with a number of me- to the talc formulation of IBA. In their japanese stewartia. They applied an dium ingredients and different combi- experiment with japanese stewartia, antioxidant (ascorbic acid) and/or nations. Spongberg and Fordham Struve and Lagrimini (1999) did not a peroxidase inhibitor (caffeic acid) to (1975) rooted stewartia in a medium find it necessary to treat the cuttings the base of the cuttings before treat- comprising of 1 perlite : 1 sand (by with any fungicide before rooting hor- ing them with a low IBA concentra- volume). Perkins and Bassuk (1995) mone treatment. Curtis et al. (1996) tion (100 mgÁL–1 quick dip). They successfully rooted japanese stewartia also did not use any disinfectant for reported that semihardwood cuttings in 1 soil : 2 peat : 1 perlite (by volume) mountain camellia cuttings. In general, of japanese stewartia taken in August medium. Of all the medium ingredi- stewartias are free of any insect and and treated with caffeic acid + IBA or, ents tested, peat and perlite are the disease problems. ascorbic acid + IBA, significantly in- most common ones. Commercial IBA and a-napthaleneacetic acid creased the rooting percentages to mixes in different combination have (NAA) are the most commonly used 67% and 64%, respectively. Curtis also been tested (Nair et al., 2008). growth regulators for induction of et al. (1996) rooted mountain camellia Curtis et al. (1996) rooted cuttings of rooting. Rooting hormones are ap- using IBA (quick dip) prepared with mountain camellia in 1 peat : 3 perlite plied as powders or liquid formula- 50% isopropyl alcohol. Their results (by volume) and got 95% rooting. tions. Cuttings of korean stewartia demonstrated that IBA concentration Gouveia (1991) obtained 80% rooting (Gouveia, 1991) and mountain camel- of 2000 and 4000 mgÁL–1 produced rates while propagating korean stew- lia (Curtis et al., 1996) can be easily 95% rooting. artia in 2 perlite : 1 sand (by volume) rooted by a quick dip application The combining of rooting hor- medium. method. Spongberg and Fordham mones has also been reported to in- Nitrogen is one of the primary (1975) reported that IBA, which can crease overwinter survival in japanese elements needed for proper growth be applied as a liquid quick dip or as stewartia. Nair et al. (2008) tested and development in plants. Nitro- a talc formulation, was the best root- four rooting hormone treatments: gen level in the medium not only ing stimulant for japanese stewartia. control, 8000 mgÁL–1 KIBA (quick influences the adventitious rooting The concentration of the rooting dip), 8000 mgÁL–1 IBA (powder), but also the shoot growth after root- hormone is also important. The use of and a combination of 5000 mgÁL–1 ing (Haissig, 1986). Different levels

• April 2010 20(2) 279 REVIEWS of nitrogen fertilization significantly carbohydrate reserves accumulated in daylength (greenhouse). She reported affected survival percentages and new the previous season (Quinlan, 1969). no effect of acclimation treatments on shoot initiation of sweetgum [Liquid- Overwinter survival of rooted cut- cutting survival, budbreak, or stem ambar styraciflua (Rieckermann et al., tings was greatly enhanced due to elongation; however, at the time of 1999)]. Curtis et al. (1996) rooted increased budbreak and shoot growth final evaluation, all the cuttings softwood cuttings of mountain ca- brought out by incandescent light + were dead. Even though there were mellia in three mediums: pine bark, CO2 treatment (Loach and Whalley, no prominent effects of acclimation pine bark + dolomitic lime, and pine 1975). New shoot growth on the observed, it would be important to bark + dolomitic lime + potassium rooted cutting contributes toward gradually acclimate the cuttings in the nitrate + Esmigran (minor element increased radial growth of the stem fall to lower temperatures before additive; Scott Company, Marysville, (Wilson and Struve, 2004). The storage. OH) + 0N–17P–0K fertilizer. Nitro- added radial growth could lead to The temperature and duration of gen at 0, 50, 100, or 200 mgÁL–1 was the development of a phellogen or storage are important factors influ- also incorporated. Cuttings rooted in endodermis (Clarkson and Robards, encing the overwinter survival of cut- pine bark medium (unamended) and 1975), which in turn will be able to tings. Stewartia usually survives and pine bark + dolomitic lime had better protect the underlying vascular tissue grows when overwintered at 1 C for overwinter survival rates (82% and and prepare and protect the cutting 3 to 4 months (Fordham, 1982). For 83%, respectively) compared with for winter. Thus, inducing budbeak japanese stewartia, an overwintering cuttings rooted in pine bark + dolo- on rooted cuttings could be an excel- temperature of 5 C has been recom- mitic lime + fertilizers (61% overwin- lent option to enhance the overwinter mended to provide a satisfactory chill- ter survival). There was no interaction survival of the cuttings. ing requirement and overwinter between medium amendments and N Budbreak can be induced through survival rate (Nair et al., 2008). Curtis rate on overwinter survival; however, the application of plant growth regu- et al. (1996) studied the effect of N increased shoot growth the follow- lators. Perkins and Bassuk (1995) overwintering storage duration on ing season, especially for the un- reported that in japanese stewartia, overwinter survival of mountain ca- amended pine bark medium. growth was significantly increased mellia rooted cuttings. The best over- Fertilizers other than N have also by silver thiosulphate + GA4/7 treat- winter survival was recorded at 6 C been tested. Smalley and Avanzato ment. However, the increased shoot and a chilling duration of 10 weeks. (1992) rooted cuttings of tall stew- growth was not critical for survival. Budbreak and shoot growth were artia in 1 peat : 2 perlite (by volume) This means that the carbohydrate positively related to the weeks of medium amended with different reserves, after rooting, were not criti- chilling. This result indicates that levels of gypsum. They concluded cally low for cuttings that did not chilling temperature and chilling du- that with the increasing concentra- exhibit significant shoot growth. It is ration are important for overwinter tion of gypsum there was a reduction believed that carbohydrate reserves survival and continued postoverwin- in the number of roots and an increase are more important than achieving ter growth of mountain camellia. in average root length. However, budbreak to insure overwinter survival In tall stewartia, bark splitting there was no significant difference in (Smalley et al., 1987). Perkins and was observed in cuttings that failed the survival rates among treatments. Bassuk (1995) determined that cut- to overwinter successfully (Smalley tings of japanese stewartia that grew and Lindstrom, 1991). Poor over- Carbohydrate storage after rooting did not have higher winter survival in difficult-to-over- and budbreak carbohydrate concentrations than winter species cannot be attributed The most widely stated reason those that did not grow. to a single factor and it varies among for poor establishment and low over- species. For example, in japanese winter survival of some deciduous Cold acclimation and stewartia, the chilling temperature re- taxa such as maple, dogwood (Cornus quirement could be one of the im- spp.), and numerous others, is the overwinter storage portant factors needed for successful low carbohydrate content in cuttings temperature overwinter survival, while it was (Loach and Whalley, 1975; Smalley Preparation for the onset of low found that for witchhazel, carbohy- et al., 1987; Waxman, 1965). The temperature is an important factor in drate reserves played a more critical process of rooting consumes sizable the growth and survival of woody role (Perkins and Bassuk, 1995). In amounts of carbohydrates. Loach and plants (Grace, 1987). In nature, the our preliminary studies, most of the Whalley (1975) postulated that the living bark of many woody plant cuttings did put forth new flush in the depleted carbohydrate levels can be species acclimates to cold in two spring but ultimately withered off. replenished if the cuttings start to grow stages during the autumn: cold accli- Cuttings of stewartia that did not before the overwinter period. Only mation and freeze tolerance (Irving overwinter showed foliar necrosis and cuttings having sufficient amount of and Lanphear, 1967). After rooting stem decay near the base close to carbohydrates by the end of winter japanese stewartia cuttings under ex- the medium (A. Nair and D. Zhang, would be able to produce a robust tended daylength, Haynes (1999) ac- unpublished data). The taxa, whose and healthy spring growth that is ex- climated the cuttings under three stems have high phenolic content tremely important for survival (Levitt, conditions: decreasing daylength and such as stewartia, may exhibit decay- 1980; Quinlan, 1969). temperature (outside), decreasing ing symptoms (browning) in their The resumption of spring growth daylength and constant temperature roots. Further experiments con- in woody plants depends on the (greenhouse), or constant extended ducted in our laboratory targeted

280 • April 2010 20(2) specific aspects like rooting hormone, Conclusion behind the absence of stewartia in rooting medium, and overwintering Many of the studies available in horticulture trade will benefit con- temperature and reported satisfactory the literature were conducted to sumers and the industry. Stewartias results (Nair et al., 2008). tackle a specific propagation aspect certainly exhibit traits and features that are desirable in our landscapes. Micropropagation of stewartia. Each study investigated a particular aspect of propagation Some of the issues related to such as medium composition, rooting sexual and asexual propagation tech- hormone, etc. and provided pieces of Literature cited niques that impede stewartia propaga- information that could be used to Clarkson, D.T. and A.W. Robards. 1975. tion are low seed viability, seedling solve the bigger puzzle of overwinter The endodermis, its structural develop- variability, and poor overwinter sur- survival. An outcome of those studies ment and physiological role, p. 415–436. In: J.G. Torrey and D.T. Clarkson (eds.). vival. Therefore, micropropagation was a better understanding of the appears to be an ideal choice for The development and function of roots. overall processes that govern or in- Academic Press, London. circumventing the abovementioned fluence the overwintering process in problems related to conventional stewartia. It is evident that overwinter Curtis, D.L., T.G. Ranney, F.A. Blazich, propagation techniques. A large num- survival of stewartia is controlled by and E.P. Whitman. 1996. Rooting and berofplantscouldbegeneratedand subsequent overwinter survival of stem a number of factors and that if opti- plants generated are true to type. cuttings of Stewartia ovata. J. Environ. mum conditions are provided, stew- McGuigan et al. (1997) cultured Hort. 14:163–166. artia can be propagated. Ironically, single node explants of japanese stew- even after two decades of research DeWolf, G.P. 1969. The introduction of artia on an agar-solidified woody initiatives, propagation of stewartia our hardy stewartias. Arnoldia 29:41–48. plant medium (WPM) amended with is still considered to be a challenge two growth regulators: N-(3-methyl- Dirr, M.A. 1998. Manual of woody land- 2-butenyl)-1H-purin-6-amine (2iP) and lacks a clear, definite solution. scape plants: Their identification, ornamen- The important fact to recognize tal characteristics, culture, propagation or N-phenyl-N-1, 2, 3-thiadiazol-5- and uses, 5th ed. Stipes, Champaign, IL. ylurea (TDZ) at different concentra- at this point is that the overwinter tions. Explants taken at the softwood success rates reported in most of the Dirr, M.A. and A.E. Richards. 1989. stage had less contamination and studies are lower than the industry Cutting propagation of Hamamelis greater budbreak than explants taken standards. A higher rate of overwinter ·intermedia ‘Arnold Promise’. Plant from more mature stem tissue. Shoot survival is needed for an economically Propagator 1:9–10. elongation was also highest in ex- viable propagation program. Even Dirr, M.A. and C.W. Heuser. 1987. The plants taken from softwood stock with the current information on stew- reference manual of woody plant propa- plant. It was notable that budbreak artia, there are not many greenhouses gation. Varsity Press, Athens, GA. was highest for explants cultured on or nurseries that are actively pursuing stewartia propagation. This could be Donnelly, J.R. and H.W. Yawney. 1972. WPM on 48.2 mM 2iP. Explants cul- Some factors associated with vegetatively tured on medium containing TDZ due to difficulties associated with propagating sugar maple by stem cut- as the growth regulator exhibited propagation or lack of consumer de- tings. Proc. Intl. Plant Prop. Soc. 22: reduced budbreak, less vigorous mand. Of the numerous research 423–430. projects undertaken to mitigate prop- growth, and appeared stunted. Effect Drew, J.J., M.A. Dirr, and A.M. Armitage. of the position of the explant (axillary agation difficulties in stewartia, the aspect of overwinter survival is the 1993. Effects of fertilizer and night in- node position) did not influence bud- terruption on overwinter survival of break frequency or shoot elongation. most critical and needs further atten- rooted cuttings of Quercus L. J. Environ. McGuigan et al. (1997) also reported tion. In addition, to get a better un- Hort. 11:97–101. no significant effect of axillary node derstanding of issues pertaining to Ekstrom, D.E. and J.A. Ekstrom. 1988. position and incorporation of GA3 on stewartia, we suggest an extensive survey of various nursery and green- Propagation of cultivars of Stewartia, budbreak or shoot elongation. Acer palmatum and Fagus sylvatica for Although japanese stewartia was house growers who are involved in open ground production. Proc. Intl. Plant propagated successfully by micropro- stewartia propagation/production. Prop. Soc. 38:180–184. pagation, large numbers of plantlets To determine impediments that hin- were not achieved because explants der market availability of stewartia, Flemer, W. 1982. Propagating shade trees feedback obtained from growers and by cuttings and grafts. Proc. Intl. Plant produced only one microcutting per Prop. Soc. 32:569–579. nodal segment (McGuigan et al., industry personnel would help re- 1997). A factor that needs to be searchers correctly determine the core Fordham, A.J. 1982. Stewartia: Propaga- addressed is the possibility of interfer- problem and formulate strategies and tion data for ten taxa. Proc. Intl. Plant ence due to polyphenolic compounds, conduct studies to address them. No Prop. Soc. 32:476–481. as plants belonging to Theaceae family matter how easy or difficult it is to Gislerod, H.R. 1983. Physical conditions are known to possess high concentra- propagate, industry feedback and co- of propagation media and their influence tion of polyphenols. Thus, before the operation is imperative to the avail- of the rooting of cuttings. III. The effects micropropagation protocol is applica- ability and popularization of any of air content and temperature in different ble to a commercial situation, more woody plant species. The landscape propagation media on the rooting of studies need to be undertaken to re- industry always has a steady demand cutting. Plant Soil 75:1–14. solve the outstanding issues related to for new plants and cultivars, and Goodman, M.A. and D.P. Stimart. 1987. micropropagation. a better understanding of reasons Factors regulating overwinter survival of

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