Potentilla rivalis
Potentilla holmgrenii
brook cinquefoil, brook or river cinquefoil, river cinquefoil, streambank cinquefoil
Holmgren's cinquefoil
stout, columnar, at least partly 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, 0.2–0.8 dm, lengths 1.5–2.5 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.
1.5–4 cm;
petiole 0.5–2 cm, long hairs absent or sparse to common (less so than cottony hairs), ± appressed, 1–2 mm, soft, smooth, cottony hairs dense, other hairs and glands absent, sparse, or obscured;
leaflets touching to overlapping, central broadly elliptic to obovate, 0.7–1.1 × 0.5–0.6 cm, sessile or short-petiolulate, petiolule to 1 mm, base cuneate, margins revolute, distal 1/2–3/4 incised ± 1/2 to midvein, teeth 2–4 per side, approximate, surfaces ± dissimilar, abaxial white to grayish white, long hairs 1 mm, cottony-crisped hairs dense, adaxial grayish green to grayish white, long and short-crisped hairs abundant to dense.
0–1.
(5–)20–100+-flowered.
1–2(–3)-flowered.
0.2–1(–2) cm.
0.4–0.7 cm in flower, to 2 cm 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 to narrowly elliptic, 2–2.2 × 0.6–0.9 mm, 1/4–1/2 as wide as sepals, margins flat, red glands absent;
hypanthium 1.8–2.2 mm diam.;
sepals 3–3.5 mm, apex subacute;
petals 4–5 × 2.5–4 mm, longer than sepals;
filaments 1–1.5 mm, anthers 0.5 mm;
carpels 30–40, apical hairs absent, styles narrowly columnar, not or ± papillate-swollen in proximal 1/5 or less, 1.2–1.4 mm.
yellowish, 0.7–0.9 mm, ± smooth, without a corky protuberance.
1.1–1.4 mm.
= 14, 70.
Potentilla rivalis
Potentilla holmgrenii
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 holmgrenii is known only from the Schell Creek and Snake ranges, Nevada, and Deep Creek Range, Utah. In addition to characteristics given in the key, lateral leaflets and leaflet teeth of P. holmgrenii are directed more forward than in P. nivea, leaflets are thicker and more densely hairy, and the terminal tooth is often orbiculate and frequently overlapped by the adjacent pair of lateral teeth.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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