CROP REPORTS 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. 138 ● January–March 2002 12(1) 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 ● January–March 2002 12(1) 139 CropRpts 139 11/27/01, 11:30 AM CROP REPORTS 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.