Geum rivale
Geum virginianum
benoîte des ruisseaux, chocolate-root, purple avens, water avens
cream avens, cream or Virginia or pale avens, cream-color avens
30–85 cm, sparsely downy to scattered-hirsute proximally, downy distally.
25–110 cm, puberulent and hirsute to densely hirsute, some hairs 2–2.5 mm.
basal 6–40 cm, blade interruptedly pinnate, major leaflets 5–7, mixed with 7–14 minor ones, terminal leaflet slightly larger than major laterals;
cauline 2–10 cm, stipules ± free, 7–18 × 5–9 mm, blade pinnate to 3-foliolate.
basal 12–25 cm, blade simple or pinnate, major leaflets 3–5, plus 0–4 minor basal ones, terminal leaflet slightly larger than major laterals;
cauline 4–15(–23) cm, stipules ± free, 11–48 × 6–35 mm, blade 3-foliolate or simple and 3-lobed to unlobed.
2–8-flowered.
3–14-flowered.
densely downy, some hairs glandular.
puberulent, sometimes with scattered hairs, eglandular.
nodding;
epicalyx bractlets 2–4 mm;
hypanthium greenish maroon to maroon;
sepals erect, 7–10 mm;
petals erect, yellow, suffused with purple and purple-veined, spatulate-obovate, 8–10 mm, ± equal to sepals, apex rounded, truncate, or shallowly emarginate.
erect;
epicalyx bractlets 1–1.5 mm;
hypanthium green;
sepals spreading but soon reflexed, 3–6 mm;
petals spreading, cream, oblong to elliptic, (1.5–)2–3.5 mm, shorter than sepals, apex rounded.
on 4–10 mm stipes, densely bristly.
sessile, densely bristly, hairs 1–2.3 mm.
geniculate-jointed, proximal segment persistent, 5–9 mm, apex hooked, stipitate-glandular, bristles on basal 1/2, distal segment deciduous, 3–4.5 mm, pilose except apical 1 mm.
geniculate-jointed, proximal segment persistent, (3–)4.5–7 mm, apex hooked, glabrate, distal segment deciduous, 1–2 mm, pilose in basal 1/2, hairs much longer than diam. of style.
= 42.
Geum rivale
Geum virginianum
Geum rivale forms hybrids with three other species of the genus in North America: G. ×aurantiacum Fries ex Scheutz [G. aleppicum × G. rivale] is reported from Alberta, Ontario, Montana, and New York; G. ×pervale B. Boivin [G. macrophyllum var. perincisum × G. rivale] is known from Alberta, Ontario, Quebec, and Saskatchewan; and G. ×pulchrum Fernald [G. macrophyllum var. macrophyllum × G. rivale] is reported from Ontario, Quebec, Idaho, New Hampshire, and Vermont. The hybrids generally have the habit and foliage of G. rivale but exhibit shallower hypanthia, spreading sepals, and pure yellow, clawed, obovate to suborbiculate petals. The glandular hairs on the pedicels usually lack the dark tips seen in G. rivale. Given that the morphologic differences among the three named hybrids are vague, suspected hybrid specimens are best determined while in the field where collectors can note the proximity of the hybrids to their supposed parental species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Geum virginianum has been confused nomenclaturally with G. laciniatum. B. L. Robinson and M. L. Fernald (1908) and J. K. Small (1933) misapplied the name G. virginianum to the species correctly named G. laciniatum, and they used the names G. flavum (Robinson and Fernald) and G. hirsutum (Small) for what is correctly named G. virginianum. Much of what is named G. virginianum in older herbarium collections is actually G. laciniatum.
In habit and leaf form, Geum virginianum is similar to G. canadense. Geum virginianum differs in having cream petals shorter than the sepals (versus white and usually equal to or longer), the largest stipules of the cauline leaves 20–48 × 10–35 mm (versus smaller), and the stems hirsute to densely hirsute (versus glabrate to downy with only scattered longer hairs). The variability within G. canadense is so great that for some specimens it is difficult to determine whether they belong to G. canadense or G. virginianum.
L. A. Raynor (1952) believed Geum virginianum to be an F1 hybrid between G. aleppicum and G. canadense. K. R. Robertson (1974) acknowledged that some herbarium specimens assignable to G. virginianum from the area where G. aleppicum and G. canadense are sympatric have mostly aborted pollen and may represent natural hybrids. He pointed out that farther south, where G. aleppicum is absent, specimens of G. virginianum appear fully fertile and seem to represent a valid species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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