Potentilla rivalis
Potentilla modesta
brook cinquefoil, brook or river cinquefoil, river cinquefoil, streambank cinquefoil
modest cinquefoil
usually not 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 to nearly erect, (0.3–)0.5–1.5(–2.5) dm.
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.
usually palmate, rarely also ternate on same plant or subpalmate, 2–6(–8) cm;
petiole 0.5–3.5(–5) cm, long hairs common to abundant, ± ascending to almost spreading, 1–2 mm, weak to ± stiff, scarcely to ± verrucose, short and/or crisped hairs common to abundant, cottony hairs absent, glands sparse to common;
leaflets (3–)5, proximalmost separated by 0–1 mm, central obovate to oblanceolate-elliptic, 0.5–2(–2.5) × 0.5–1(–1.5) cm, petiolules 1 mm, distal 3/4 to nearly whole margin incised 1/2–3/4 to midvein, teeth 2–5 per side, (1–)2–5 mm, apical tufts 0.5–1 mm, abaxial surfaces white, long hairs common to abundant, cottony-crisped hairs dense, short hairs and glands absent or obscured, adaxial grayish green, long hairs common to abundant, 0.5–1.5 mm, ± stiff, rarely soft, short and/or crisped hairs sparse to common, cottony hairs absent, glands sparse to common.
1–2.
(5–)20–100+-flowered.
(1–)3–10-flowered, congested or ± elongating in fruit, branch angle 20–35°.
0.2–1(–2) cm.
0.2–0.5 cm, proximal to 1.2 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, 1.5–3 × 0.5–1 mm;
hypanthium 3–4 mm diam.;
sepals 2.5–4 mm, apex ± acute, glands abundant, usually not obscured;
petals yellow, ± overlapping, 3.5–5 × 3–4 mm, slightly longer than sepals;
filaments 1 mm, anthers 0.3–0.7 mm;
carpels 20–40, styles 1 mm.
yellowish, 0.7–0.9 mm, ± smooth, without a corky protuberance.
1 mm.
= 14, 70.
Potentilla rivalis
Potentilla modesta
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 modesta is the dominant component of what has previously been called P. rubricaulis in the Intermountain Region (for example, N. H. Holmgren 1997b, including illustration). This and other species of alpine Potentilla often grow in mixed populations, which contributes to confusion and mistaken identifications. In general, P. modesta has a more compact inflorescence and more consistently palmate basal leaves than sympatric members of the section. Intergrades with P. jepsonii (sect. Pensylvanicae) can also be problematic, though leaves of the latter are generally subpinnate and abaxially grayish rather than white.
The epithet modesta is misapplied in the combination Potentilla concinna var. modesta, which S. L. Welsh et al. (1993) used for plants mostly placed here in P. concinna var. divisa (sect. Concinnae).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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