Potentilla rivalis
Potentilla hippiana
brook cinquefoil, brook or river cinquefoil, river cinquefoil, streambank cinquefoil
Hipp's cinquefoil, horse cinquefoil, potentille de Hipp, woolly 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.
(0.3–)2–4(–5) dm, lengths (1–)2–4 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 to subpinnate, (3–)5–15(–25) cm;
petiole 1–10(–15) cm, long hairs abundant to dense, tightly appressed, 1–2.5 mm, stiff, short hairs absent or obscured, crisped-cottony hairs absent or sparse to common, glands absent or obscured;
leaflets not conduplicate, lateral ones evenly (to unevenly in argyrea phase) paired, (2–)3–6(–7) per side on distal (1/6–)1/5–1/2 of leaf axis, distal pairs ± decurrent, often confluent with terminal leaflet, larger leaflets oblanceolate or narrowly obovate to oblong, 1–5(–6) × 0.3–1.5 cm, distal (2/3–)3/4 to whole margin incised 1/2 or less (rarely more) to midvein, teeth (5–)7–12(–18) per side, 1–4 mm, surfaces ± to strongly dissimilar, abaxial white, long hairs abundant (mostly on, but not limited to, veins), 1–2 mm, stiff, short hairs absent or obscured, crisped-cottony hairs abundant to dense, glands absent or obscured, adaxial green to grayish, long hairs sparse to common, rarely absent, short or crisped to, sometimes, cottony hairs absent or sparse to common, glands sparse.
1–2(–3).
(5–)20–100+-flowered.
10–30-flowered.
0.2–1(–2) cm.
0.3–3(–5) 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 narrowly elliptic to lanceolate, rarely linear, 2–5 × 0.5–1.5 mm, (1/2–)2/3 as long as sepals, abaxial vestiture similar to or ± sparser than sepals, usually not glabrescent, straight hairs ± abundant, crisped to sometimes ± cottony hairs absent or sparse to abundant;
hypanthium 3–7 mm diam.;
sepals 4–5.5(–6.5) mm, apex acute to acuminate;
petals 4–8 × 4–7 mm;
filaments 0.5–2.5 mm, anthers 0.6–1.1 mm;
carpels (5–)10–30, styles 1.7–2.5 mm.
yellowish, 0.7–0.9 mm, ± smooth, without a corky protuberance.
1.4–1.8 mm, smooth to faintly rugose.
= 14, 70.
= 42, 70, 77, 84, 98.
Potentilla rivalis
Potentilla hippiana
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.)
Potentilla hippiana is most common and distinctive in the Colorado Plateau and southern Rocky Mountains, with outliers in the mountains of Arizona, Nevada, and New Mexico. Occurrences are more scattered in the northern Rocky Mountains and Great Plains, where intergradation with P. effusa is common. Among these intermediates are the argyrea phase and the single report from Idaho (B. C. Johnston 1980). Potentilla hippiana is probably adventive in Nova Scotia, eastern Ontario, Quebec, and Michigan, and possibly the Northwest Territories. The reported occurrence in central Alaska (E. Hultén 1968) is based on a specimen of P. pensylvanica (CAN).
Significant variation exists throughout the range of Potentilla hippiana, including dwarfism, leaf division, leaflet dissection, adaxial leaflet vestiture, and pedicel length. Some of this variation might merit taxonomic recognition upon further analysis, especially if correlated with ploidy level (6x through 12x). At present, the differences used to distinguish var. argyrea are not found to be sufficiently correlated with distribution to merit formal taxonomic recognition.
Complicating the infraspecific variation is a tendency for Potentilla hippiana to intergrade with other species, in particular P. effusa. Beyond sect. Leucophyllae, the frequency of hybrids with P. pulcherrima blurs the distinction between the two species; P. gracilis var. hippianoides S. L. Welsh & N. D. Atwood is probably one of the resultant intermediates.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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