Potentilla rivalis |
Potentilla lasiodonta |
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brook cinquefoil, brook or river cinquefoil, river cinquefoil, streambank cinquefoil |
Sandhills cinquefoil |
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Stems | decumbent to erect, sometimes prostrate, (0.5–)1–4(–7) dm, hairs at base not stiff, not tubercle-based, glands absent or sparse, inconspicuous. |
± erect, 2–4 dm. |
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. |
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Basal leaves | pinnate, 12–20(–30) cm; petiole 5–10(–15) cm, long hairs ± abundant, spreading to ascending, 0.5–1 mm, weak to ± stiff, short hairs abundant to dense, cottony or crisped hairs absent, glands sparse to abundant, often obscured; leaflets 4–6(–9) per side, on distal (1/3–)1/2–3/5 of leaf axis, slightly overlapping, terminal ones oblanceolate to narrowly elliptic, 3–6 × 0.8–1.2(–1.5) cm, margins strongly revolute, incised ± 1/2 to midvein, undivided medial blade 5–9 mm wide, teeth 8–12 per side, narrowly triangular to lanceolate, surfaces ± dissimilar, abaxial grayish, long hairs ± sparse (or not differentiated from short hairs), 0.5–1.5 mm, weak, short hairs abundant to dense, cottony or crisped hairs absent, glands sparse or obscured, adaxial ± green, straight hairs (long and short not differentiated) abundant, spreading to ascending, 0.2–0.5 mm, cottony and crisped hairs absent, glands sparse to abundant, often obscured. |
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Cauline leaves | (1–)2–4. |
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Inflorescences | (5–)20–100+-flowered. |
10–40-flowered, congested or elongating in fruit. |
Pedicels | 0.2–1(–2) cm. |
± 0.1 cm (proximal to 1.2 cm). |
Flowers | 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 ovate-acuminate, (3–)4–8(–10) × 2–3 mm, lengths 1–2 times sepals, margins ± revolute; hypanthium (4–)5–10 mm diam.; sepals 3–5 mm, apex acute to obtuse, abaxial surfaces: venation moderate, glands ± abundant, obscured to evident; petals pale yellow, 3–5 × 2–4 mm, lengths ± equal to or shorter than sepals; filaments 1–1.5 mm, anthers 0.5–0.8 mm; carpels 80–90, styles papillate-swollen in proximal 3/4+, 1–1.2 mm. |
Achenes | yellowish, 0.7–0.9 mm, ± smooth, without a corky protuberance. |
± 1 mm, ± rugose. |
2n | = 14, 70. |
= 14. |
Potentilla rivalis |
Potentilla lasiodonta |
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Phenology | Flowering spring–summer. | Flowering summer. |
Habitat | Moist meadows, stream banks, lakeshores, gravel bars in flood plains, drying marshes, open areas in river-bottom forests | Sandy sites in prairies |
Elevation | 200–2400 m (700–7900 ft) | 300–1100 m (1000–3600 ft) |
Distribution |
AZ; CA; CO; IA; ID; IL; KS; MA; MD; ME; MN; MO; MT; ND; NE; NM; NV; NY; OK; OR; SD; TX; UT; VA; WA; WI; WY; AB; BC; MB; ON; SK; Mexico (Baja California)
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MN; ND; AB; MB; SK |
Discussion | 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 lasiodonta is a diploid relative of tetraploid P. pensylvanica, sharing similar velvety vestiture of dense short hairs, pinnate leaves, and epicalyx bractlets with revolute margins. The species differs in having larger epicalyx bractlets and less deeply incised leaflets. Plant height and leaf size are at the upper range of P. pensylvanica, and populations are evidently restricted to sandy substrates. Occurrence in Manitoba is based on B. L. Kohli and J. G. Packer (1976); no vouchers are in WIN. At least one collection from southeastern British Columbia (Brown 779, MO) approaches P. lasiodonta, but it is insufficient by itself to serve as a provincial record. The fundamental ploidy and epicalyx distinctions of this species were established by B. L. Kohli and J. G. Packer (1976), who proposed the name Potentilla finitima. As noted by J. Soják (1994), the type of P. lasiodonta is the same entity. Potentilla atrovirens Rydberg and P. pensylvanica var. arida B. Boivin have sometimes been applied to this taxon; the types of both names fall within the circumscription of P. pensylvanica in the narrow sense (Packer, pers. comm.). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 9, p. 139. | FNA vol. 9, p. 214. |
Parent taxa | Rosaceae > subfam. Rosoideae > tribe Potentilleae > Potentilla > sect. Rivales | Rosaceae > subfam. Rosoideae > tribe Potentilleae > Potentilla > sect. Pensylvanicae |
Sibling taxa | ||
Synonyms | P. millegrana, P. pentandra, P. rivalis var. millegrana, P. rivalis var. pentandra | P. finitima |
Name authority | Nuttall: in J. Torrey and A. Gray, Fl. N. Amer. 1: 437. (1840) | Rydberg: in N. L. Britton et al., N. Amer. Fl. 22: 351. (1908) |
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