Potentilla thurberi
Potentilla vulcanicola
scarlet cinquefoil, Thurber's cinquefoil
stout, sometimes ± columnar, not sheathed with marcescent whole leaves.
(2–)3–7(–10) dm.
ascending to erect, (0.2–)0.4–1.6(–2) dm, lengths 2–3 times basal leaves.
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.
1–6(–11) cm;
petiole 0.5–4(–9) cm, long hairs ± abundant, ascending to spreading, sometimes loosely appressed, 1–2.5 mm, soft to weak, smooth, crisped(/cottony) hairs absent or sparse, sometimes common, glands absent or sparse;
leaflets overlapping, central broadly obovate, 0.8–2(–2.5) × 0.8–1.5(–2.5) cm, sessile or subsessile, base broadly cuneate, margins strongly revolute, distal 1/2–2/3 incised ± 1/2 to midvein, teeth 2–3(–4) per side, distant, surfaces strongly dissimilar, abaxial grayish white, long hairs 1–2 mm, cottony-crisped hairs ± dense, adaxial usually dark green, sometimes grayish green, long hairs sparse to abundant, other hairs usually absent.
stipules usually toothed, sometimes entire.
(0–)1–2(–3).
(4–)10–35-flowered.
1–2(–5)-flowered.
0.5–4 cm.
1–2 cm in flower, to 5 cm in fruit.
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 ± oblong to ovate, 4–8(–10) × 1.8–3(–5) mm, 2/3 to as wide as sepals, margins revolute, sometimes flat, red glands absent;
hypanthium 3.5–4.5 mm diam.;
sepals 5–8 mm, apex ± acute;
petals 7–9 × 7–10 mm, longer than sepals;
filaments 0.8–1 mm, anthers 0.6–0.7 mm;
carpels 20–30, apical hairs sparse to abundant (straight), styles conic-columnar, ± papillate-swollen in less than proximal 1/5, or sometimes to 1/5, 0.8–1.1 mm.
1.5 mm, ± rugose.
0.9–1.2 mm.
= 28 (Russian Far East).
Potentilla thurberi
Potentilla vulcanicola
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.)
Potentilla vulcanicola is close morphologically to P. uniflora in the narrow sense and largely replaces it in southern and eastern Chukotka, Alaska, and northwestern Canada, where it reaches east of Mackenzie River on the coastal mainland and the westernmost islands (Banks and Victoria islands). Potentilla subgorodkovii and P. vulcanicola account for a major part of North American records of P. uniflora.
(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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