Flora of North America species comparison

Varieties 2 (2 in the flora).

Characters useful in recognizing specimens of Geum macrophyllum are yellow petals, epicalyx bractlets often absent, proximal style segment sparsely to densely stipitate-glandular, and fruiting receptacles puberulent. Across its broad North American range from Alaska to California and Nova Scotia, G. macrophyllum exhibits considerable variation. Based largely on the shape of the terminal leaflet of the basal leaves and the degree of dissection and shape of the divisions of the distal cauline leaves, P. A. Rydberg (1913b) distinguished three species within the range of variation treated here as one species. Basal leaves of G. macrophyllum in the strict sense (var. macrophyllum in this treatment) have relatively large reniform to rounded terminal leaflets and the distal cauline leaves are three-cleft into rhombic or cuneate lobes. The basal-leaf terminal leaflets of G. perincisum (= var. perincisum) are only slightly larger than the laterals and are deeply lobed into rhombic-obovate segments; the distal cauline leaves are dissected into oblanceolate divisions. Both basal and cauline leaves of G. oregonense (= var. perincisum) are intermediate between those of G. macrophyllum and G. perincisum. W. Gajewski (1955) crossed all three taxa under discussion and examined leaf morphology and cytology of the F1 and F2 hybrids. He concluded that they were distinct but not yet completely separated species. Fairly well correlated with the more dissected leaves of G. oregonense and G. perincisum is the presence of minute stalked glands on the pedicels. The treatment here follows H. M. Raup (1931) in recognizing two varieties of G. macrophyllum based more on pedicel glandularity than leaf morphology.

(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.)