Plant Genera


Crocanthemum

Family Code: CISTAC
Genus Code: CROCA
Genus CN: Frostweed, Rockrose
Genus Summary: A genus of about 24 species, of eastern North America, California, Mexico, and s. South America. The eastern North American species previously attributed to Helianthemum are in a clade distinct from the Old World Helianthemum, and should be recognized as Crocanthemum.
Genus Identification: Identification notes: The identification of most of our species of Crocanthemum requires an understanding of the 2 types of flowers produced. Chasmogamous flowers have showy yellow petals and larger sepals, the distinct portion of the 2 linear outer sepals usually linear, (0.7-) 1.3-5.5 mm long, the distinct portion of the 3 broader inner sepals 2.5-12 (-14) mm long. Cleistogamous flowers lack petals and have smaller sepals, the distinct portion of the 2 linear outer sepals 0.2-3 mm long, the distinct portion of the 3 broader inner sepals 1.5-4.8 mm long. In some species (C. canadense, C. bicknellii, C. propinquum) the chasmogamous flowers open earlier (Apr-Jul) than the cleistogamous (Jun-Sep). In others (C. corymbosum, C. georgianum, C. nashii, C. rosmarinifolium), the two types of flowers open at the same time (Mar-Jun) or cleistogamous flowers are nearly always absent (C. carolinianum). Capsules from chasmogamous flowers are larger and contain more seeds than those from cleistogamous flowers.
Genus References: Sorrie in FNA (2015); Daoud & Wilbur (1965)=Z; Wilbur & Daoud (1964)=Y; Arrington & Kubitzki in Kubitzki & Bayer (2003).
Last Updated: 2019-11-30
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