Flora of North America species comparison

Varieties 2 (2 in the flora).

At the beginning of the twentieth century, E. L. Greene described over a dozen species belonging to the Geum triflorum complex based on differences in leaf form and indument, the relative length and shape of the epicalyx bractlets and sepals, and petal length and shape. Most of these species were quickly reduced to synonymy by other botanists. When specimens are examined from across the continent, most of the characters used to separate species in the G. triflorum complex show nearly continuous variation. It seems best to treat these variants as belonging to one species. Whether and how to classify the variation within the species will remain controversial. Some character expressions correlate reasonably well with dividing the species into two varieties, as was first proposed by N. C. Fassett (1928). Variety triflorum occurs east of the Rocky Mountains and is typical of the grasslands covering the northern Great Plains; it also is the variety found in the mountains of Arizona and New Mexico. Variety ciliatum is common throughout the rest of the Rocky Mountains, the Sierra Nevada, and Cascade Range. Intermediate specimens occur here and there, particularly in Alberta and British Columbia.

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

In the broad area where their ranges overlap, Geum aleppicum is often confused with G. macrophyllum var. perincisum. The two taxa are similar in habit and leaf form and they occupy the same habitats. Mixed collections mounted on one herbarium sheet are sometimes seen. One macroscopic clue useful in quickly sorting herbarium specimens is the color of the dried plants. Geum aleppicum often, but not always, darkens considerably upon drying and appears blackish green; G. macrophyllum is lighter and greener. In G. aleppicum, the epicalyx bractlets are always present and conspicuous; the bractlets are relatively small or absent in G. macrophyllum. In fruiting specimens, the styles of G. aleppicum have bristles at the base and are without glands; the styles of G. macrophyllum lack bristles and are nearly always stipitate-glandular. The bristles at the base of the style are a consistent and useful characteristic in fruiting specimens of G. aleppicum. Other species of avens may have bristles on the achenes; no others (except for occasional specimens of G. laciniatum) have bristles on the styles.

Geum aleppicum hybridizes with G. rivale (= G. ×aurantiacum Fries ex Scheutz); see discussion under 8. G. rivale.

Geum strictum Aiton is a superfluous and illegitimate name for G. aleppicum.

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