American columbo (Frasera caroliniensis) COSEWIC assessment and status report: chapter 5

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Species Information

• Name and Classification
• Morphological Description
• Genetic Description

Name and Classification

American columbo was first described as Frasera caroliniensis Walter, but many subsequent authors have included Frasera Walter within the cosmopolitan genus Swertia L. (e.g. Fernald, 1950). A worldwide revision of Swertia is needed to resolve this issue (Crins and Sharp, 1993). Most recent eastern North American floras (e.g. Wofford, 1989; Gleason and Cronquist, 1991; Voss, 1996) recognize Frasera at the generic rank. No author has disputed the validity of Frasera caroliniensis Walter as a species.

Morphological Description

Frasera caroliniensis is a robust perennial herb with a thick taproot. Each year it produces a basal rosette of 3-25 oblong deciduous leaves. Reproductive individuals form a single flowering stem 2-3 m tall. Stem leaves grow in whorls of 4(5), the lower similar to those of non-flowering rosettes and up to 40 cm long, the upper progressively shorter. The pyramidal inflorescence is composed of long-pedunculate cymes arranged in whorls from the upper axils (Figure 1). The four petals are united at the base, forming a saucer-shaped greenish-yellow flower 10-20 mm long, with numerous dark spots or streaks. Each petal is yellow below its middle with a large circular gland conspicuously fringed along the margins. The fruit is a compressed ellipsoid capsule 1.5-2 cm long. Capsules contain 4-14 dark brown, crescent-shaped winged seeds (Crins and Sharp, 1993 and references therein). Individual plants flower only once, after 7-15 or more years of growth, as discussed below.

Frasera caroliniensis is unmistakeable in flower and fruit. The fruiting stems may be up to 3m tall and persist for a year or more (Threadgill et al., 1981a). Illustrations appear in Threadgill et al. (1981a), Holmgren et al. (1998), and on the United States Department of Agriculture Plants website, http://plants.usda.gov/ (USDA NRCS, 2002).

Genetic Description

No genetic assessment of this species has been conducted.

Figure 1: Frasera caroliniensis

Britton and Brown, 1913.