Potentilla rivalis
Potentilla hookeriana
brook cinquefoil, brook or river cinquefoil, river cinquefoil, streambank cinquefoil
graceful cinquefoil, Hooker's cinquefoil
not sheathed with marcescent whole leaves.
decumbent to erect, sometimes prostrate, (0.5–)1–4(–7) dm, hairs at base not stiff, not tubercle-based, glands absent or sparse, inconspicuous.
ascending to nearly erect, (0.3–)0.5–2 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.
usually both ternate and palmate on same plant, rarely subpalmate, 1–9 cm;
petiole 0.5–6 cm, long hairs common to abundant, ± appressed to ascending-spreading, (0.5–)1–1.5(–2) mm, usually stiff, rarely weak, verrucose, short-crisped hairs sparse to common, cottony hairs absent, glands ± sparse;
leaflets 3–5, proximalmost separated by 0(–1) mm, central oblanceolate to obovate, 0.5–2.5 × 0.4–1.2 cm, petiolules 0–1 mm, distal ± 3/4 of margin incised 1/2–3/4, rarely +, to midvein, teeth 2–6 per side, 1–5 mm, apical tufts 0.5–1 mm, abaxial surfaces grayish white to white, long hairs common to abundant, cottony-crisped hairs usually dense, short hairs and glands absent or obscured, adaxial green to grayish green, long hairs sparse to common, 0.5–1.5 mm, usually stiff, short and/or crisped hairs sparse to common, cottony hairs absent, glands sparse to common.
1–2.
(5–)20–100+-flowered.
1–6(–8)-flowered, open, branch angle 20–50°.
0.2–1(–2) cm.
(0.5–)1–2 cm, proximal to 3 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 linear to oblong-lanceolate, 2–3 × 0.7–1.3 mm;
hypanthium 3–4 mm diam.;
sepals 3–5 mm, apex subacute, glands ± common, not obscured;
petals yellow, ± overlapping, 3–6(–7) × 4–5 mm, usually longer than sepals;
filaments 0.5–1.5 mm, anthers 0.3–0.5 mm;
carpels 30–50, styles 0.8–1.2 mm.
yellowish, 0.7–0.9 mm, ± smooth, without a corky protuberance.
1–1.3 mm.
= 14, 70.
Potentilla rivalis
Potentilla hookeriana
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.)
As here defined, Potentilla hookeriana consists of primarily alpine plants from the Rocky Mountains and adjacent desert mountains that share many of the same characters with P. rubricaulis but are smaller overall. Arctic plants previously included in P. hookeriana are now assigned to P. arenosa (J. Soják 1986; B. Ertter et al. 2013).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
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MD Biodiversity, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria, Turner Photog. 
WildflowerSearch
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