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.)

Geum vernum is distinctive and is recognized by its early flowering, minute petals, lack of epicalyx bractlets, and heads of achenes soon elevated well beyond the recurved hypanthia and sepals. Recently, it has been expanding its range northward and has been collected with increasing frequency in southern Ontario, Massachusetts, Michigan, New York, and Wisconsin. No specimens could be located to confirm reports of G. vernum from Mississippi or Texas.

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