Potentilla rivalis
Potentilla basaltica
brook cinquefoil, brook or river cinquefoil, river cinquefoil, streambank cinquefoil
Black Rock potentilla, Soldier Meadow or Black Rock cinquefoil, soldier meadows 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, sometimes ascending in supporting vegetation, 1.5–5 dm, lengths 2–3 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, 5–12(–18) × 1–1.5(–2) cm;
petiole 0.5–1(–1.5) cm, straight hairs absent, cottony hairs absent, glands absent or sparse;
primary lateral leaflets (5–)10–15(–20) per side, on nearly whole leaf axis, ± overlapping, largest ones (or leaflet lobes) elliptic, 0.4–1(–2) × 0.2–0.5(–1) cm, simple and entire or 2(–3)-fid to base (sometimes shallowly toothed as well), segments 1–2(–3), narrowly to broadly elliptic, 4–10(–20) × (1–)2–3 mm, apical tufts absent or less than 0.5 mm, surfaces green, glaucous, straight hairs absent or sparse to common, tightly appressed, 0.5 mm or less, stiff, cottony hairs absent, glands absent or sparse.
2–4.
(5–)20–100+-flowered.
(5–)10–20-flowered, loosely cymose.
0.2–1(–2) cm.
0.8–3(–4) cm, straight to ± 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 lanceolate-elliptic to ovate-elliptic, 1.5–2.5(–3) × 1 mm;
hypanthium 2–5 mm diam.;
sepals (3–)4–5(–6) mm, apex acute to acuminate;
petals (3.5–)4.5–6.5 × 2.5–4 mm;
filaments 1.5–3 mm, anthers 0.6–0.8 mm;
carpels 3–10, styles 2–2.5 mm.
yellowish, 0.7–0.9 mm, ± smooth, without a corky protuberance.
1.8–2.2 mm, smooth to ± rugose, not carunculate.
= 14, 70.
Potentilla rivalis
Potentilla basaltica
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 basaltica is very distinctive in its glaucous, highly divided cylindric leaves with leaflets arranged in four ranks. The leaves strongly resemble those of some species of Ivesia, especially I. kingii S. Watson, but molecular analysis (B. Ertter et al. 1998) confirms a relationship with other members of sect. Multijugae.
Potentilla basaltica is known from only two localities, one in Lassen County, California, and the other in Humboldt County, Nevada. Both populations are highly localized, and P. basaltica is a candidate for federal listing as well as of conservation concern in both states.
The epithet basaltica was chosen as a reference to the Black Rock Desert, not habitat.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
Go Botany, 
IL Wildflowers, 
KS Wildflowers, 
MD Biodiversity, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria, Turner Photog. 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
