Potentilla thurberi
Potentilla brunnescens
scarlet cinquefoil, Thurber's cinquefoil
brownish cinquefoil, slender brown cinquefoil, slender cinquefoil
conspicuous, usually golden.
(2–)3–7(–10) dm.
ascending to nearly erect, (1.5–)3–7 dm.
palmate, (2–)4–15(–30) cm;
petiole (2–)3–10(–25) cm, long hairs sparse to common, spreading, 1–3.5 mm, weak, glands sparse to abundant, sometimes absent;
leaflets 5(–7), at tip of leaf axis, central one (1–)2–6(–8) × (0.5–)1–2.5(–4) cm, petiolules 0(–10) mm, distal 3/4 to whole margin incised 1/5–1/4 to midvein, teeth (4–)7–15(–19) per side (sometimes secondarily toothed), (1–)2–3(–5) mm, teeth apex acute to ± obtuse, surfaces slightly to strongly dissimilar, abaxial pale green to white, straight hairs sparse to abundant, often dense on veins, 0.5–3 mm, cottony hairs absent or sparse to dense, glands ± sparse or absent, sometimes obscured, adaxial green, straight hairs sparse to abundant, 0.2–1 mm, cottony hairs absent, glands ± sparse or absent.
sometimes 2-ranked, palmate, (5–)10–30 cm;
petiole (1.5–)5–25(–50) cm, long hairs sparse to abundant, appressed to spreading, 1–2 mm, ± stiff, short, crisped, and cottony hairs absent, glands ± abundant;
leaflets (5–)7–9, at tip of leaf axis, separate to slightly overlapping, largest ones oblanceolate-elliptic to narrowly obovate, (2–)5–10 × 1–4 cm, margins flat to ± revolute, distal 3/4 to nearly whole length ± evenly incised (1/4–)1/2–3/4+ to midvein, undivided medial blade 2–15(–20) mm wide, teeth (5–)7–10 per side, linear to broadly lanceolate, 3–15 mm, surfaces ± similar, abaxial paler, green, not glaucous, long hairs sparse to common, short-crisped hairs absent or sparse, cottony hairs absent, glands ± abundant.
stipules usually toothed, sometimes entire.
1–3(–4).
(4–)10–35-flowered.
12–30(–70)-flowered.
0.5–4 cm.
0.2–1(–4) cm.
epicalyx bractlets narrowly to broadly lanceolate-elliptic (rarely toothed or lobed), 4–9(–14) × (1–)1.5–2 mm;
sepals 4–10(–15) mm, apex acute to acuminate;
petals ± dark reddish throughout, (3.5–)6–10 × 6–10 mm;
filaments 1.5–3 mm, anthers 0.8–1 mm;
carpels 30–70, styles 2.5–3.5 mm.
epicalyx bractlets lanceolate to elliptic, 3–6 × 1–2 mm, hairs sparse to common, loosely appressed to spreading, glands common to abundant;
hypanthium 4–6(–8) mm diam.;
sepals 4–8(–9) mm, apex acute to acuminate;
petals 6–9 × 6–10 mm;
filaments 1–2 mm, anthers 0.6–1 mm;
carpels 30–60, styles filiform-tapered, papillate-swollen proximally, 1.5–2 mm.
1.5 mm, ± rugose.
1.5 mm.
Potentilla thurberi
Potentilla brunnescens
Varieties 2 (2 in the flora).
The abaxially white-cottony leaflets of var. atrorubens usually make it easily distinguished from var. thurberi, which lacks cottony hairs and is usually less hairy in general. The two varieties sometimes occur together and intermediates between the extremes are common.
The degree of glandularity and the lengths of the central leaflets are greater in the southern populations of both varieties. The glands are less widely distributed on the plants northward and are fewer in northern Arizona and New Mexico. Leaflets are shorter and broader north of Graham County, Arizona, and Otero County, New Mexico.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The conspicuous golden glands, dark green color, and relatively broad leaflets make Potentilla brunnescens one of the better-defined species of sect. Graciles, though it has often been treated as a variety of P. gracilis. The glands, which are often on septate stalks, are particularly conspicuous on the epicalyx bractlets, hypanthium, and sepals, and at the junction of petiole and leaflets. The species occurs from the Blue Mountains of Oregon and Washington to western Montana, northern Utah, and north-central Colorado; collections from Alaska are probably not native.
As presented here, Potentilla brunnescens encompasses two morphological extremes that might merit varietal status. Leaflets of the more common and widespread extreme are incised about halfway to the midvein; in contrast, some populations in western Wyoming and adjacent Idaho have leaflets incised 3/4 or more to the midvein. The latter have often been assigned to P. gracilis var. elmeri while reserving P. gracilis var. brunnescens for the former; this is untenable because the type of P. brunnescens is the latter form.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaflets pale green abaxially, cottony hairs absent. | var. thurberi |
1. Leaflets ± white to white abaxially, cottony hairs sparse to dense. | var. atrorubens |
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