Potentilla rivalis
Potentilla hyparctica
brook cinquefoil, brook or river cinquefoil, river cinquefoil, streambank cinquefoil
arctic cinquefoil, subarctic 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.
ascending to erect, 0.2–2(–2.5) dm, lengths 1–3(–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.
not in ranks, ternate, (1–)2–8(–10) cm;
stipules: apex ± acute;
petiole 1–6.5(–8.5) cm, long hairs sparse to common, spreading to subappressed, 0.8–2 mm, weak to ± stiff, glands sparse to common;
leaflets 3, central obovate to broadly obovate, 0.5–2.5(–2.8) × 0.3–2(–2.2) cm, petiolule 0–3 mm, margins flat or slightly revolute, not lobed, distal 1/2–2/3(–3/4) evenly incised ± 1/2 to midvein, teeth (2–)3–5 per side, surfaces ± similar, abaxial usually pale green, sometimes grayish, hairs sparse to abundant, 0.5–1.7 mm, adaxial darker green, hairs and glands sparse.
(5–)20–100+-flowered.
1–3(–5)-flowered.
0.2–1(–2) cm.
straight, 0.3–3 cm in flower, to 9 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 narrowly to broadly oblong or ovate, 3.5–7 × 1.5–5 mm, margins flat;
hypanthium 4–7 mm diam.;
sepals 4–8 mm, apex subacute to rounded;
petals pale or bright yellow, 4–9 × 4–6 mm;
filaments 0.5–1.1 mm, anthers 0.2–0.4 mm;
carpels 50–80, styles ± columnar, not or scarcely papillate-swollen proximally, 0.6–0.9 mm.
yellowish, 0.7–0.9 mm, ± smooth, without a corky protuberance.
1.1–1.3 mm.
= 14, 70.
Potentilla rivalis
Potentilla hyparctica
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.)
Subspecies 3 (2 in the flora).
Southern arctic and subarctic plants differ from the northern arctic ones in presumably independent features. Where the two forms are sympatric (western Greenland, northern Quebec, Baffin Island), they appear to remain distinct even in mixed populations and are accordingly treated as subspecies.
Although some features of scattered plants in Alaska and Yukon approach subsp. nivicola Jurtzev & V. V. Petrovsky (described from northeastern Asia), such plants do not otherwise correspond fully with this taxon. Possible hybrids between Potentilla hyparctica and P. pulchella (sect. Pensylvanicae) are addressed in the discussion of sect. Pensylvanicae. Presumed hybrids with P. villosa from the Aleutian Islands, characterized by the combination of basally thickened styles and lack of cottony hairs on leaflet abaxial surfaces, have been named P. ×aleutica Soják.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Epicalyx bractlets narrowly to ± oblong or ovate, 1.5–2 mm wide; central leaflets: petiolules 0–2 mm, bases cuneate. | subsp. hyparctica |
1. Epicalyx bractlets broadly oblong or ovate, 2–5 mm wide; central leaflets: petiolules (0–)2–3(–5) mm, bases broadly cuneate to rounded. | subsp. elatior |
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