Potentilla rivalis
Potentilla multijuga
brook cinquefoil, brook or river cinquefoil, river cinquefoil, streambank cinquefoil
Ballona cinquefoil, lost 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.
prostrate to ascending, 2–5(–7) dm, lengths 1–2 times basal leaves.
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.
pinnate with distal leaflets ± confluent, 10–22 × 1.5–3.5 cm;
petiole (2–)4–10 cm, straight hairs absent or sparse, appressed, 0.5–1.5 mm, stiff, cottony hairs absent, glands absent;
primary lateral leaflets 3–8 per side, on distal 1/3–2/3 of leaf axis, ± separate, largest ones cuneate to obovate, 1–2.2 × 0.8–1.5 cm, distal 1/3–2/3 of margin ± evenly incised ± 1/2 to midvein, ultimate teeth 3–6, ± ovate, 2–6 × 1.5–3 mm, apical tufts absent, surfaces green, not glaucous, straight hairs sparse to nearly absent (except on margins), ± appressed, 0.5–1 mm, stiff, cottony hairs absent, glands absent or sparse.
1–3.
(5–)20–100+-flowered.
3–10(–20)-flowered, very openly cymose, sometimes racemiform.
0.2–1(–2) cm.
1.5–3.5(–5) cm, ± recurved in fruit.
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 ovate-elliptic, 2.5–4(–5) × 1.5–3 mm, sometimes toothed;
hypanthium 4–6 mm diam.;
sepals 4–6(–7) mm, apex acute, rarely acuminate;
petals 4.5–10 × 4–10 mm;
filaments 1.5–3(–4.5) mm, anthers 0.7–1 mm;
carpels 5–10, styles 2–3 mm.
yellowish, 0.7–0.9 mm, ± smooth, without a corky protuberance.
1.8–2 mm, smooth to faintly rugose, possibly carunculate.
= 14, 70.
Potentilla rivalis
Potentilla multijuga
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.)
Of conservation concern.
Potentilla multijuga is known only from a handful of collections made in the 1890s near the current site of Los Angeles International Airport. All efforts to locate extant plants have failed; the species is presumed extinct. Continued use of P. multijuga for this species required conservation of the name with a conserved type, because the type designated by Lehmann is a specimen of Horkelia cuneata Lindley var. cuneata (B. Ertter and J. L. Reveal 2008).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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PNW Herbaria, Turner Photog. 
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