Flora of North America species comparison

Varieties 2 (2 in the flora).

Even with the recognition of Crocanthemum aldersonii and C. suffrutescens as separate species, morphological diversity within C. scoparium still remains considerable. The two varieties here recognized show differences in habit, average plant height, number of flowers, and distribution. Another variant occurs sporadically along the coast and on Santa Cruz Island, from Monterey to San Diego counties; vegetative parts (at least distal branches, pedicels, and sepals) are covered with white, lanate hairs. This variant has never been formally named. Another form from coastal Mendocino County was called “Helianthemum mendocinensis” by Alice Eastwood on a specimen (H. E. Brown 785, JEPS); the name was never published. These plants have densely stellate-pubescent stems and exceptionally elongate sepal tips.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Crocanthemum dumosum occurs in nine coastal counties. Crocanthemum dumosum and C. canadense are closely related; the former inhabits specialized, maritime environments. They can be distinguished in the field by the ascending or divaricate, relatively numerous stems of C. dumosum, often giving it a bushy aspect (versus erect, single or relatively few stems, and nonbushy); leaf surfaces dull under dense stellate hairs in C. dumosum (versus lustrous under sparser stellate hairs). Identification of occasional plants may be equivocal; those are a small minority.

Using AFLP markers, S. G. Obae et al. (2013) found that Crocanthemum dumosum nested within the same cluster as C. canadense. The authors “recommend that it be considered as a subspecific variant of C. canadense,” but did not make a new combination. Additional molecular work warranted to solidify their findings.

(Discussion copyrighted by Flora of North America; reprinted with permission.)