Potentilla rivalis
Potentilla rhyolitica
brook cinquefoil, brook or river cinquefoil, river cinquefoil, streambank cinquefoil
decumbent to erect, sometimes prostrate, (0.5–)1–4(–7) dm, hairs at base not stiff, not tubercle-based, glands absent or sparse, inconspicuous.
0.2–2 dm.
ternate, palmate, or subpalmate (with distal leaflets ± confluent), basal 3–15(–25) cm, cauline 2–7(–12) cm;
petiole: basal 1–9(–16) cm, cauline 0.5–4(–8) cm, long hairs usually common to abundant, ascending to spreading, 0.5–1.5 mm, usually ± weak, ± crisped hairs common to abundant, glands absent or sparse, inconspicuous;
leaflets 3–5(–7), at tip to distal 1/5 (basal) or 1/2 (cauline) of leaf axis, separate to ± overlapping, largest ones oblanceolate-elliptic to obovate, (0.5–)1–5(–6) × 0.5–2(–2.5) cm, distal 1/2–3/4 of margin evenly to unevenly incised 1/3–1/2 to midvein, sometimes cleft nearly to base, teeth 3–8 per side, surfaces moderately to abundantly hairy, glands absent or sparse.
ternate, rarely palmate, 2–8(–11) cm;
petiole 1–6(–8) cm, long hairs abundant to dense, spreading to loosely appressed, 1–2(–3) mm, weak to ± stiff, glands ± abundant;
leaflets 3(–5), central obovate to broadly elliptic, 1–3 × 0.8–1.8 cm, often distinctly petiolulate, distal 1/2–2/3 of margins evenly incised ± 1/3 to midvein, teeth 2–3(–4) per side, surfaces green to gray-green, long hairs common to dense, 1 mm, glands abundant.
(5–)20–100+-flowered.
1–10-flowered.
0.2–1(–2) cm.
0.5–1(–2) cm.
epicalyx bractlets narrowly elliptic to ovate, (1.5–)2–4(–6) × 0.8–1.5 mm;
hypanthium (2–)3–5 mm diam.;
sepals 3–5 mm, apex broadly acute to obtuse;
petals pale yellow to yellow, broadly oblong-obovate, 1.5–2 × 1 mm;
stamens (5–)10(–15), filaments 0.4–0.9 mm, anthers 0.2–0.3 mm;
carpels 40–100, styles 0.5–0.6 mm.
epicalyx bractlets lanceolate-elliptic, 2–4 × 1 mm;
hypanthium 3–5 mm diam.;
sepals 3–5 mm, apex acute;
petals ± paler abaxially, bright yellow adaxially, ± obcordate, 3–7 × 2–5 mm;
filaments 1.5–3 mm, anthers 0.6–1 mm;
carpels 5–15, styles 2–3 mm.
yellowish, 0.7–0.9 mm, ± smooth, without a corky protuberance.
1.5–2 mm, smooth to lightly rugose.
hairs not well differentiated from long hairs, absent or sparse throughout.
= 14, 70.
Potentilla rivalis
Potentilla rhyolitica
Potentilla rivalis is most abundant in central and western North America; reports of occurrences in more eastern states (including those listed here) need confirming, as P. rivalis and P. norvegica often have been confused. Potentilla leucocarpa Rydberg was provided as a superfluous replacement name for P. millegrana; specimens annotated by Rydberg with this name include both P. biennis and P. rivalis.
Potentilla rivalis is sometimes divided into three species or varieties (for example, H. J. Scoggan 1978–1979). In a strict sense, var. rivalis has subpalmately compound (5-foliate) leaves. Variety milligrana, the most common phase, has 3-foliate leaves. Plants with both 3- and 5-foliolate leaves are var. pentandra, which also tends to have five stamens, though this latter character is not correlated with the leaf features. On the Great Plains, where var. pentandra is confined, all three expressions are often found in a single population (R. L. McGregor 1986b).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (2 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaves gray-green, hairs usually dense, sometimes common; styles 2–2.5 mm; achenes 1.5 mm, smooth to lightly rugose; Santa Rita and Huachuca ranges. | var. rhyolitica |
1. Leaves green, hairs common, rarely dense; styles (2–)2.5–3 mm; achenes 2 mm, smooth; Chiricahua Range. | var. chiricahuensis |
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BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
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KS Wildflowers, 
MD Biodiversity, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria, Turner Photog. 
WildflowerSearch
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