Geum rossii
Geum urbanum
alpine avens, Ross' avens, slender stem avens
benoîte commune, clover-root, colewort, herb-bennet, town avens, wood avens
4–28 cm, glabrous or downy, hairs to 1 mm, sometimes septate-glandular.
25–85 cm, puberulent and sparsely hirsute.
basal 3–13 cm, blade pinnate to interruptedly pinnate, major leaflets 13–26, alternating with 0–14 minor ones, terminal leaflet slightly larger than major laterals;
cauline 0.7–2 cm, stipules adnate to leaf, indistinguishable from pair of lobes, blade bractlike, not resembling basal, alternate, simple, pinnatifid to 3-fid.
basal 12–25 cm, blade strongly lyrate-pinnate to pinnate, major leaflets 1–9, sometimes alternating with minor ones, terminal leaflet slightly to much larger than major laterals;
cauline 4–15 cm, stipules ± free, 10–40 × 5–35 mm, blade pinnate, 3-foliolate, or simple and 3-lobed.
1–3(–4)-flowered.
3–18-flowered.
woolly, sometimes glandular.
puberulent, less densely hirsute, eglandular.
erect;
epicalyx bractlets 1.5–7 mm;
hypanthium green, slightly purple-tinged to strongly purple;
sepals erect to erect-spreading, 3–10 mm;
petals spreading, yellow, obovate to nearly orbiculate, 5–12(–17) mm, longer than sepals, apex broadly rounded to irregularly emarginate.
erect;
epicalyx bractlets 0.5–2 mm;
hypanthium green;
sepals spreading but soon reflexed, 2–5 mm;
petals spreading, yellow, suborbiculate, elliptic, or obovate, 2–6 mm, shorter to longer than sepals, apex rounded.
sessile, glabrous.
sessile, densely bristly, hairs 1–2.3 mm.
wholly persistent, not geniculate-jointed, 2–5(–10) mm, apex not hooked, glabrous throughout or pilose only at base.
geniculate-jointed, proximal segment persistent, 3–7 mm, apex hooked, glabrous, distal segment deciduous, 1–1.5 mm, glabrous or with short hairs, hairs shorter than diam. of style.
= 56.
= 42.
Geum rossii
Geum urbanum
The variability accommodated here in Geum rossii was distributed by earlier monographers such as P. A. Rydberg (1913b) and F. Bolle (1933) among a half dozen species. W. Gajewski (1957) reduced them to two species, G. rossii and G. turbinatum; most recent taxonomists have recognized the two taxa as subspecies or varieties of a single species. The large geographic discontinuity between the Rocky Mountain and arctic ranges makes it easy for those wishing to follow this tradition. No one morphologic character or combination of characters neatly separates the arctic plants from those of the Rockies.
Where their ranges overlap in Alaska, Geum rossii hybridizes with G. calthifolium to form sterile plants known as G. ×macranthum (Kearney ex Rydberg) B. Boivin; see discussion under 4. G. schofieldii.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Specimens from Chicago, Illinois, and Cambridge, Massachusetts, indicate that Geum urbanum has been present in North America for at least 100 years; herbarium specimens are scarce. The species seems to be spreading in ruderal habitats of the northeastern United States and adjacent Canada. The plants have the habit and foliage of G. canadense and G. virginianum, with stipules as large as or even larger than those of the latter; the petals are bright yellow versus white or cream, and the distal segments of the styles are glabrous or nearly so versus partially pilose.
Geum urbanum is often found growing near G. canadense, and the two occasionally form hybrids; G. ×catlingii J.-P. Bernard & R. Gauthier is known from New Brunswick, Ontario, Quebec, and Michigan. Less common is G. ×macneillii J.-P. Bernard & R. Gauthier [G. laciniatum × G. urbanum], known from Quebec. Both hybrids closely resemble G. urbanum in vegetative form, with little hint of their other parent; it is likely that hybrid plants often go undetected. Most herbarium specimens of these hybrids were collected along with their parental species at the same locality. The hybrids are often robust, apparently showing hybrid vigor. Unlike G. urbanum, they have cream petals and heads with mostly sterile ovaries.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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BC, 
OR, 
WA - Local Web sites:
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Flora NW, 
PNW Herbaria 
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