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Classification, origin, and environmental requirements Stokes aster initially was described and classified as Carthamus laevis by J. Hill in 1769. The genus Stokesia was Crop described by L’Héritier de Brutelle (1788), who proposed that the type specimen used by J. Hill to describe C. laevis should be selected as the type Reports specimen for the new genus Stokesia. L’Héritier de Brutelle (1788) also re- ferred to S. cyanea but failed to describe the species; therefore, the name S. cyanea is illegitimate. The final authority re- Stokes Aster (12,13-epoxy-cis-9-octadecenoic) garding the nomenclature of stokes as- acid, a fatty acid that is converted to ter is Greene (1893), who stated that epoxy oil products for use in the manu- the proper binomial for the specimen 1 facture of plastics and adhesives called C. laevis by J. Hill and S. cyanea by Lyn A. Gettys and (Campbell, 1981; Kleiman, 1990). Oil L’Héritier de Brutelle should be Stokesia Dennis J. Werner2 content in seeds can be as high as 40%, laevis. The genus is named for the En- with about 70% of this oil being vernolic glish botanist Jonathan Stokes (1755- acid (Gunn and White, 1974). In the 1831). 1980s, the annual global market for Stokesia is one of about 950 genera ADDITIONAL INDEX WORDS. Stokesia seed-derived epoxy oils was between laevis, Asteraceae, Vernonieae, oilseed in the aster family (Asteraceae Dumont) crop, native plant, propagation 45 and 90 billion tons (40.8 and 81.6 and is monotypic, with S. laevis the only × 109 t) per year (Campbell, 1981; species (Bailey, 1949; Els, 1994; Greene, Princen, 1983). The United States 1893; Gunn and White, 1974). Stokesia alone currently uses between 50 and belongs to the subfamily Tubiliflorae tokes aster [Stokesia laevis 75 billion tons (45.4 and 68.0 × 109 t) within the tribe Vernonieae Cass. (J. Hill) Greene] is an under- of epoxy oil on an annual basis Vernonieae has two other genera— S used herbaceous perennial that (Cunningham, 1997). Most of this is Elephantopus L. and Vernonia Schreb. has great potential use as a landscape derived from traditional petrochemi- Stokesia is the only member of the ornamental and as an industrial oilseed cals and the processing of linseed and Vernonieae tribe that is restricted to the crop. It has large, showy flowers and is soybean oils. Cultivation of stokes as- United States. Stokesia can be separated available in several attractive cultivars. ter as an oilseed crop could reduce the from the other genera in the tribe based Grown primarily for its flowers (Bailey, amount of petrochemicals used in this on the large 3- to 4-inch (7.6- to 10-cm) 1949), it has been described as a species process while providing an alternative, of minor ornamental importance in the sustainable source for raw material Fig. 1. Plant of stokes aster ‘Purple southeastern United States (Gunn and (Gunn and White, 1974; White, 1977). Parasols’ in flower. White, 1974). Huxley (1992) recom- mended its use both as a cut flower and as an ornamental landscape plant. Stokes aster also has potential use as an oilseed crop because its seeds contain large amounts of vernolic
Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609. This research was funded in part by the North Carolina Agricultural Research Service (NCARS) and the Peren- nial Plant Association. This paper is a portion of a thesis submitted by Lyn A. Gettys in partial fulfillment of the requirements for the MS degree. The authors wish to thank R. Evinger of Niche Gardens in Chapel Hill, N.C., for crop scheduling protocols. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by N.C. State Univ. and does not imply its approval to the exclusion of other products or vendors that might also be suitable. 1Graduate research assistant. Current address: Univ. Fla., IFAS–FLREC, 3205 College Ave., Ft. Lauder- dale, FL 33314. 2Professor.
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CropRpts 138 11/27/01, 11:30 AM diameter inflorescence and enlarged Radford et al., 1964), and is thought to in or slightly above the vegetative canopy. marginal flowers; in addition, the pap- be a facultative intermediate-day plant The composite inflorescences of pus of Elephantopus and Vernonia is (Clough et al., 1999). Facultative inter- stokes aster (Fig. 2) have multiple per- permanent, while the pappus of Stokesia mediate-day plants achieve most consis- fect flowers forming each capitulum. is early deciduous (Gunn and White, tent and rapid flowering when exposed Flowers in native populations range in 1974). to a photoperiod of 12 to 13 h. Con- color from blue to bluish-purple or Stokes aster is indigenous to south- flicting information is published in the bluish-violet to white (Bailey, 1949; eastern North America (Bailey, 1949; literature and popular press regarding Gunn and White, 1974). Gunn and Gunn and White, 1974). Native popu- the conditions necessary to induce floral White (1974) reported that white-flow- lations are concentrated in South Caro- initiation. Campbell (1984) suggested ered taxa are seldom found in natural lina, southern Mississippi, Louisiana, that vernalization may be necessary for populations. The composite flower heads southern Alabama, and Florida (Bailey, floral development and that plants placed of stokes aster are typically 3 to 4 inches 1949; Gunn and White, 1974; Huxley, in the landscape in spring may not pro- in width (Bailey, 1949; Liberty Hyde 1992). Isolated colonies in southern duce flowers until summer of the fol- Bailey Hortorium, 1976). In vivo polli- South Carolina, central Georgia, and lowing year. Clough et al. (1999) stated nation of stokes aster is entomophilous, the Florida Panhandle are found in areas that seed-derived plants of stokes aster with pollen transferred primarily by bees. that are damp to wet for at least part of will not produce flowers during the The cypsela (more commonly referred the year (Gunn and White, 1974). initial year of growth due to a period of to as the seed) is the product of an L’Héritier de Brutelle (1788) stated juvenility. They also reported that a cold inferior ovary. that the specimen he called S. cyanea is treatment is not necessary for floral de- Disagreement exists as to whether native to South Carolina. Stokes aster is velopment in mature plants, and opti- the capitulum, or composite inflores- classified as hardy in USDA hardiness mum flowering is dependent upon pho- cence, is composed of disc flowers only zones 5–8 (Brickell, 1992) and Ameri- toperiod. Highest flowering percentage or of both ray and disc flowers. Bailey can Horticultural Society heat zones 4– of stokes aster occurred when plants (1949) and Steyermark (1963) stated 8 (Cathey, 1998). DeFreitas (1987) were grown with a photoperiod of 12 to that all plants in the Vernonieae tribe, of stated that stokes aster can thrive into 13 h. Floral initiation in seed-derived which stokes aster is a member, have southern Florida (USDA hardiness breeding populations is highly variable disc flowers only. Bailey (1949) also zones 10B–11). Brickell (1992) stated (Werner and Gettys, unpublished data). stated that enlarged disc flowers along that stokes aster is fully hardy, meaning Some genotypes were actively flowering the species can withstand subfreezing 5 months after seeds were sown, while Fig. 2. Mature inflorescence of stokes temperatures during the winter without others required more than 1 year to aster ‘Klaus Jelitto’. significant damage, but Coughlin flower. (1991) recommended that protective measures, such as the application of Botanical several inches of mulch, be taken in description regions that experience freezing and Stokes aster is an thawing. acaulescent, herbaceous Established colonies of stokes aster perennial with alternate appear to tolerate a wide range of mois- leaves that form a basal ture levels. Coughlin (1991) recom- rosette (Fig. 1). At ma- mended its use as a drought-tolerant turity, plants may be up perennial, while Brickell (1992) merely to 28 inches (70 cm) called for well-drained soil. However, tall (Gunn and White, Gunn and White (1974) and Bell and 1974; Liberty Hyde Taylor (1982) observed that stokes as- Bailey Hortorium, ter naturally inhabits moist or poorly 1976), but most culti- drained regions at the southernmost vars grow to a height of end of the plant’s range. The dichotomy 1 to 2 ft (30-60 cm). in moisture tolerance is most likely a The elliptic to lanceolate function of climate, as increased hydra- leaves are entire, thick, tion can sometimes compensate for ac- and range from 4 to 12 celerated evapotranspiration that typi- inches (10 to 30 cm) cally accompanies high air temperatures long by 0.3 to 2.0 inches found in extreme southern regions. (0.8 to 5.0 cm) wide. Stokes aster is thought to be a Leaves are grayish- shade-tolerant sun species; full sun is green. Peduncles are pu- preferable, but some shade is tolerated. bescent to woolly and Seedlings of stokes aster typically pro- may become glabrate duce only vegetative growth the first with age. Peduncle year (Callan and Kennedy, 1995; length varies among Campbell, 1981). Stokes aster flowers genotypes but most cul- from late spring through summer (Bell tivars have peduncles and Taylor, 1982; DeFreitas, 1987; that bear flower heads
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the margin of the capitulum may re- cultivars appear to have trace amounts aster; therefore, its parentage is also semble ray flowers. Greene (1893) de- of anthocyanin in the petals. Blue-flow- unknown. scribed members of the Vernonieae as ered commercially available cultivars ‘Omega Skyrocket’ exhibits a mark- being destitute of ray corollas. Gunn include ‘Blue Danube’, ‘Blue Moon’, edly different growth habit from the and White (1974) stated that stokes ‘Blue Star’, ‘Klaus Jelitto’, and ‘Wyo- species and the aforementioned culti- aster has consistently been placed in the ming’ (Brickell, 1992; Gunn and White, vars and is described as bearing laven- Vernonieae; however, they also reported 1974; Hay and Synge, 1975; Huxley, der-blue flowers on peduncles that may that capitula of stokes aster possess lin- 1992; Phillips and Burell, 1993). be up to 3.3 ft (1 m) long. At this time, ear-lanceolate ray flowers that are 1.0 to ‘Träumerei’ and ‘Maroon’ have flowers ‘Omega Skyrocket’ is available only with 1.6 inches (2.5 to 4.0 cm) long and that range in color from white tipped wild-type (bluish-violet) flower color, tubular disc flowers that are 0.4 to 0.8 with lilac to solid lilac. ‘Träumerei’ is but a white-flowered group has also inch (1.0 to 2.0 cm) long. The descrip- seed propagated. ‘Aba’ is generally of- been selected (M. Groves, personal com- tion of ray flowers in stokes aster con- fered as a seed-propagated cultivar, but munication). flicts with the Vernonieae tribal require- some nurseries propagate it vegetatively ‘Omega Skyrocket’ was derived ment for inflorescences that are com- and market a clonal selection. In addi- from a wild population of plants found posed solely of disc flowers. tion to the above cultivars, Bailey (1949) growing in Colquitt County, Ga., near The receptacle of the capitulum of listed ‘Caerulea’ and ‘Lilacina’ as having the town of Omega, by R. Determann, stokes aster is flat, fleshy, and naked. blue or lilac flowers, respectively. Nei- S. Determann, and O. Johnson of the Flower heads are showy and borne in ther is found in the trade; it is possible Atlanta Botanical Garden (R. corymbs of one to seven capitula on that these cultivars are still available Determann, Atlanta Botanical Garden, long, leafy peduncles (Gunn and White, under a different name. personal communication). The original 1974; Huxley, 1992). Six sets of bracts Many cultivars of stokes aster are population consisted of a group of plants are imbricate or tiled around the base of thought to be selections from wild or that were morphologically similar to the capitulum, tipped with spines, and garden populations, but no formal docu- one another, but possessed a growth may become inflexed at maturity to mentation exists as to how most culti- habit different from the wild type stokes facilitate cypsela retention (Gunn and vars arose. In addition, most cultivars aster. The site where ‘Omega Skyrocket’ White, 1974). Bract inflection and have characters that are only slightly originally was found has since been de- cypsela retention is variable and may different from the species. Notable ex- veloped into cultivated pastureland and differ considerably among dissimilar ceptions include ‘Mary Gregory’, ‘Purple the original population of plants has genotypes. The outermost bracts are Parasols’, ‘Honeysong Purple’, and been destroyed. Fortunately, seeds were foliaceous and not persistent after flow- ‘Omega Skyrocket’. collected from many specimens within ering. Two sets of outer bracts are also ‘Mary Gregory’ is the only known the population before habitat destruc- foliaceous; these are elliptic to lanceolate yellow-flowered cultivar of stokes aster tion; as a result, some level of germ- and range from pubescent to glabrate. and is readily available from commercial plasm preservation was established. Two sets of inner bracts are toothed to nurseries, but no formal publication of ‘Omega Skyrocket’ is primarily propa- entire; the apex may be covered with the cultivar name was found. It was gated by seed but some nurseries have tawny, crinkled hairs or may be glabrous reportedly found as a seedling in a gar- selected and offered clonal selections. with ciliate margins. The innermost den population in Columbia, S.C., by bracts are similar to the inner bracts, but M. Creel of the S.C. Dept. of Natural Pests and pest are narrow with an entire margin. Resources (M. Creel, personal commu- management nication). The patented ‘Purple Para- Cultivars Stokes aster is reportedly suscep- sols’ was selected in Kentucky and reg- tible to head blight (Botrytis cinerea The wild type, or species, of stokes istered by C.S. Warren of North Ameri- Pers. ex Fr.) and leaf spot (Ascochyta aster bears flowers that are described as can Lily and Floral in 1998 (Warren, Lib.) (USDA, 1960). Powdery mildew lavender-blue or bluish-violet. White- 1998). It is described as having flowers (Erysiphe cichoracearum DC. ex Merat) flowered specimens are rarely found in that are light blue initially, then chang- can be problematic (Ellett, 1963; wild populations (Gunn and White, ing to dark-blue, bluish-purple, red- Kilpatrick et al., 1975), as are mosaic 1974) and a yellow-flowered stokes as- dish-purple, and dark hot-pink as the virus and bidens mottle virus (Horst, ter has been found only once. Cultivars head ages. The parentage of ‘Mary Gre- 1990; Logan et al., 1984). Kilpatrick were described in the literature and gory’ and ‘Purple Parasols’ is unknown. and Uecker (1978) isolated 26 types of popular press as early as the 1940s (Bailey, ‘Honeysong Purple’ first was of- fungi growing on stokes aster, but fun- 1949); however, information concern- fered commercially in 2000 by Wayside gal infestations found in their screen- ing the origin and development of many Gardens of Hodges, S.C. (Wayside ings were primarily Alternaria alternata cultivars is unavailable. Most commer- Gardens, 2000). It is described as being Fr. ex Keissler and unidentified species cially available cultivars have vegetative ultrafloriferous and bearing deep-purple of Phomopsis (Sacc.) Bubák and growth similar to that of the species and flowers. Flower color reportedly dark- Phyllosticta Pers. Sclerotinia sclerotiorum differ only in flower color. ens as the head ages, which “…high- (Lib.) dBy. and Sclerotium rolfsii Sacc. ‘Alba’ bears white flowers (Bailey, lights the contrasting white stamens were also identified as pathogens of 1949; Hay and Synge, 1975; Huxley, and red overtones”. It was discovered stokes aster by Kilpatrick and Uecker 1992; Liberty Hyde Bailey Hortorium, by Alex and Alan Summers. Plant patent (1978), who stated that plants infected 1976; Phillips and Burell, 1993), as protection is being sought. ‘Honeysong by these fungi did not survive. Uecker does ‘Silver Moon’ (Gunn and White, Purple’ is a seedling selection from an (1989) described the development of 1974; Huxley, 1992); however, both open-pollinated population of stokes Diaporthe phaseolorum (Cooke et Ellis)
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CropRpts 140 11/27/01, 11:30 AM Sacc. on stokes aster. Other fungal The possibility of seed production by take place over an extended time, and pathogens include Stemphylium ‘Alba’ through apomixis has not been recommended a germination tempera- floridanum C.I. Hannon et Weber ruled out. Since most cultivars of stokes ture of less than 41 ºF (5 ºC). Thomp- and unidentified species of Cercospora aster are propagated using asexual son and Morgan Inc. (Suffolk, En- Fuckel and Rhizoctonia DC. (Alfieri et methods, self-incompatibility does not gland) stated that germination of stokes al., 1984). hamper production of established cul- aster seed may take up to a year. Spe- Greenhouse pests include aphids tivars. The requirement for cross-pol- cialty Perennial Seeds (Apple Valley, (Myzus persicae Sulzer and other spe- lination can, however, be viewed as a Minn.) and Germania Seed Company cies) and whiteflies (Trialeurodes limiting factor for breeding purposes, (Chicago, Ill.) recommended that seeds vaporariorum Westwood and Bemisia as the production of inbred lines for be frozen for 5 d, then sown at 60 to 65 argentifolii Bellows et Perring). Mi- use as breeding stock in a formal culti- ºF (15.5 to 18.3 ºC) for 14 to 21 d to nor infestations may be limited by var development program is virtually achieve highest germination percent- allowing adequate airflow around impossible. The self-incompatibility age. Armitage (1994) stated that high- plants, while more serious infestations found in most cultivars of stokes aster est germination percentage occurs may be controlled by application of can also be beneficial, as the system when seeds of stokes aster are stratified fungicides and pesticides labeled for eliminates the need for emasculation for 6 weeks at 39 ºF (4 ºC) and use on herbaceous perennial plants. of the maternal parent in cross-polli- germinated at 66 ºF (19 ºC). Camp-
nation events designed to produce F1 bell (1984) performed studies that Genetic analysis and hybrids. Seed production and reten- showed highest germination percent- reproductive biology tion are extremely variable and cultivar age was achieved at 68 ºF (20 ºC), and The chromosome number of dependent; also, seeds may require up he also stated that seeds did not germi- stokes aster has been established as 2n to four months of ripening after polli- nate below 52 ºF (11 ºC). Clough et = 2x = 14 (Gunn and White, 1974; nation and resultant progeny may ex- al. (1999) suggested that seeds of stokes Keeley and Jansen, 1994). All cultivars hibit a great deal of variation (Gettys, aster germinate without stratification of stokes aster are closely related to one 2000). These factors make in-house in 12 d at 70 ºF (21 ºC). More recent another, with the exception of ‘Omega seed production impractical for most evidence by Gettys (2000) showed Skyrocket’. Gettys (2000) used ran- growers. In addition, one must re- that seeds germinated in 14 to 21 d at domly amplified polymorphic DNA member that most cultivars of stokes 59 to 68 ºF (15 to 20 ºC) and that (RAPD) analysis (also called DNA fin- aster will not maintain their unique stratification was neither required nor gerprinting) to show that most pairs of characteristics when propagated by beneficial. Our studies have shown cultivars of stokes aster exhibited ho- sexual means; ‘Träumerei’, ‘Omega that seeds harvested in late summer or mology at >85% of the fragments pro- Skyrocket’, ‘Alba’ and the species may early fall can be sown immediately in duced from 74 RAPD primers, while be reliably produced from seeds. There- 612 cell packs [individual cell volume ‘Omega Skyrocket’ was homologous fore, a grower wishing to produce a 4.5 inch3 (74 cm3)] in the greenhouse with other cultivars at only 65% to 70% uniform population of stokes aster and may be transplanted to 1-qt (1-L) of these fragments. This high degree plants from seed is limited to a re- pots and moved to a protected loca- of homology suggests a limited amount stricted number of cultivars. Seed tion outside to overwinter in about 8 of genetic diversity within the species; should be purchased from a reputable weeks (unpublished data). Plants pro- however, breeding experiments by the dealer. duced in this manner should be large authors produced offspring with dis- Propagation and crop and vigorous enough to sell the fol- tinct traits not previously described, lowing spring. including overall plant size, growth scheduling Vegetative propagation of stokes habit, time of floral initiation, flower Stokes aster is typically propa- aster by root cuttings or division is morphology, and seed set. gated by seed, division, or root cut- common. Plantlets produced by divi- Information concerning the re- tings (Brickell, 1992; DeFreitas, 1987; sion will reach marketable size more productive biology of stokes aster is Hay and Synge, 1975; Hosoki et al., quickly than those derived from root limited. Anthers dehisce and pollen is 1995). Many of the unique character- cuttings; however, a single stock plant released before anthesis (unpublished istics that differentiate specific culti- may be used to produce far more plants data), but production of viable seeds vars from the species may be main- from root cuttings than from division. without cross-pollination is rare. The tained only by vegetative propagation; As much as 30% of the root mass may species is classified as self-incompat- however, the species and selected cul- be removed for use in propagation by ible (Campbell, 1981, 1984; Gunn tivars may be propagated by seed. Light root cutting without deleterious ef- and White, 1974; Kleiman, 1990; does not appear to affect germination, fects to the stock plant. Root cuttings Princen, 1983; White, 1977). Studies and germination is variable in seed may be taken at any time of year; performed by Gettys (2000) showed populations (Campbell, 1984; Clough however, cuttings taken in early spring that ‘Klaus Jelitto’, ‘Mary Gregory’, et al., 1999; Gettys, 2000). Conflict- appear to produce plantlets most reli- ‘Omega Skyrocket’, and ‘Silver Moon’ ing information is present in the litera- ably. Root cuttings taken in fall may be are self-incompatible, while ‘Alba’ is ture and the popular press regarding successful if bottom heat is used. highly self-fertile. However, no formal optimum temperature conditions for Niche Gardens (Chapel Hill, documentation or experimental evi- germination of seeds. For example, N.C.) produces plants of stokes aster dence exists regarding the mechanism Jelitto Perennial Seed Co. by root cuttings, and head propagator responsible for self-incompatibility in (Schwarmstedt, Germany) suggested R. Evinger recommends the following most cultivars and self-fertility in ‘Alba’. that germination is irregular and may protocol. Thick roots are selected and
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cut into sections 3 to 4 inches (8 to 10 Ohta. 1995. In vitro propagation of white stokesia cm) in length. Flats that are 2 to 3 Literature cited (Stokesia laevis Greene var alba hort.) by leaf and inches (5 to 8 cm) deep are filled with Alfieri, Jr., S.A., K.R. Langdon, C. Wehlburg, and root culture. J. Jpn. Soc. Hort. Sci. 64:378–380. a standard potting medium to within 1 J.W. Kimbrough. 1984. Index of plant diseases in Huxley, A. (ed.). 1992. The new Royal Horticul- inch (2.5 cm) of the top of the flat. A Florida. Bul. 11. Div. Plant Ind.,Gainesville, Fla. tural Society dictionary of gardening. Macmillan, trench is prepared in the medium and Armitage, A.M. 1994. Ornamental bedding plants. London. roots are placed in the trench at a 45º CAB Intl., Wallingford, England. Keeley, S.C. and R.K. Jansen. 1994. Chloroplast angle. Polarity is maintained so that Bailey, L.H. 1949. Manual of cultivated plants. DNA restriction site variation in the Vernonieae the proximal end of the root cutting is revised ed. Macmillan, New York. (Asteraceae), an initial appraisal of the relationship closest to the surface of the medium. of new and old world taxa and the morphology of Between 20 and 40 cuttings can be Bell, C.R. and B.J. Taylor. 1982. Florida wild Vernonia. Plant Syst. Evol. 193:249–265. flowers and roadside plants. Laurel Hill Press, placed in each trench and each flat may Chapel Hill, N.C. Kilpatrick, R.A. and F.A. Uecker. 1978. Fungi on contain up to 10 trenches, accommo- stokes aster. Can. J. Plant Sci. 58:471–473. dating several hundred root cuttings. Brickell, C. (ed.). 1992. The American Horticul- tural Society encyclopedia of garden plants. Kilpatrick, R.A., F.A. Uecker, and G.A. White. Potting medium is added to cover Macmillan, New York. 1975. Powdery mildew, a new disease of stokes each trench and bring the surface of aster. Plant Dis. Rptr. 59:795. Callan, E.J. and C.W. Kennedy. 1995. Intercrop- the medium level with the top of the Kleiman, R. 1990. Chemistry of new industrial flat. Flats are placed in a shade house ping stokes aster: effect of shade on photosynthesis and plant morphology. Crop Sci. 35:1110–1115. oilseed crops, p. 196–203. In: J. Janick and J.E. and hand-watered only two to three Simons (eds.). Advances in new crops: Proceed- times a week, as excessive moisture Campbell, T.A. 1981. Agronomic potential of ings of the first national symposium, New crops: seems to result in loss of many root stokes aster. Amer. Oil Chem. Soc. Monogr. 9:287– Research, development, economics. Timber Press, pieces. Plantlets of stokes aster pro- 295. Portland, Ore. duced in this manner are ready to be Campbell, T.A. 1984. Response of stokes aster L’Héritier de Brutelle, C.L. 1788. Sertum teased apart and transplanted to 1-qt achenes to chilling. J. Amer. Soc. Hort. Sci. Anglicum, seu plantae rariores quae in hortis juxta pots about 3 months after the root 109:736–741. Londinum, imprimis in horto regio kewensi excoluntur ab anno 1786 ad annum 1787 cuttings are placed in the flats. The Cathey, H.M. 1998. Heat-zone gardening. Time observatae. Pierre-Francois Didot, Paris. resulting plants are large enough to Life Books, New York. Liberty Hyde Bailey Hortorium. 1976. Hortus offer for sale 3 to 6 months after trans- Clough, E., A. Cameron, R. Heins, and W. Carlson. planting to 1-qt pots (R. Evinger, per- third: A concise dictionary of plants cultivated in 1999. Forcing perennials. Greenhouse Grower the United States and Canada. 3rd ed. Macmillan, sonal communication). 17(11):40–48. New York. Conclusions Coughlin, R.A. 1991. The gardener’s companion: Logan, A.E., F.W. Zettler, and S.R. Christie. A book of lists and lore. Harper Perennial, New 1984. Susceptibility of Rudbeckia, Zinnia, Agera- Stokes aster has great potential York. for increased use as a landscape orna- tum, and other bedding plants to bidens mottle virus. Plant Dis. 68:260–262. mental. The large, showy inflorescences Cunningham, I. 1997. Farmers and investors poised are appealing and numerous cultivars to benefit from competing efforts to bring new Phillips, E. and C.C. Burell. 1993. Rodale’s illus- industrial oilseed crop to the world. Diversity trated encyclopedia of perennials. Rodale Press, are available, providing a range of col- 13:34–36. ors for growers and consumers. Pro- Inc., Emmaus, Pa. duction requirements are not exact- DeFreitas, S. 1987. Complete guide to Florida Princen, L.H. 1983. New oilseed crops on the gardening. Taylor Publ. Co., Dallas, Texas. ing, as cultivars of stokes aster are easily horizon. Econ. Bot. 37:478–492. propagated by root cuttings and re- Ellett, C.W. 1963. New records of powdery mil- Radford, A.E., H.E. Ahles, and C.R. Bell. 1964. quire no special equipment, treatments, dews. Plant. Dis. Rptr. 47:289–291. Vascular flora of the Carolinas. The Book Ex- or handling. These factors make stokes Els, D. (ed.). 1994. The National Gardening change, Univ. N.C., Chapel Hill. aster a prime candidate for increased Association dictionary of horticulture. Penguin Steyermark, J.A. 1963. Flora of Missouri. Iowa attention from growers and propaga- Books, New York. State Univ. Press, Ames. tors, and an attractive perennial flow- Gettys, L.A. 2000. Investigations of optimum Uecker, F.A. 1989. A timed sequence of develop- ering plant for inclusion in the land- seed germination conditions, reproductive biol- ment of Diaporthe phaseolorum (Diaporthaceae) scape. ogy, and genetic relationships between cultivars of from Stokesia laevis. Mem. N.Y. Bot. Garden 49:38– Stokes aster also has potential for stokes aster [Stokesia laevis (J. Hill) Greene]. MS 50. use as an industrial oilseed crop with thesis. N.C. State Univ., Raleigh. U.S. Department of Agriculture. 1960. Index of great implications for the plastics and Greene, E.L. 1893. Observations on the plant diseases in the United States. USDA–ARS adhesives industries (Campbell, 1981; Compositae—I. Erythea 1(1):1–4. Agr. Hdbk. 165. Kleiman, 1990). Cultivation of stokes Gunn, C.R. and G.A. White. 1974. Stokesia laevis: aster as an oilseed crop may reduce the Warren, C.S. 1998. U.S. patent #PP010660. Taxonomy and economic value. Econ. Bot. Stokesia plant (sic) Purple Parasols. U.S. Patent amount of petrochemicals used while 28:130–135. Trademark Office, Wash., D.C. providing an alternative, sustainable Hay, R. and P.M. Synge. 1975. The colour dictio- Wayside Gardens. 2000. Online catalog, Wayside source for raw material (Gunn and nary of garden plants with house and greenhouse White, 1974; White, 1977). Stokes Gardens, Hodges, S.C. 11 Dec. 2000.
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