64. Potentilla flabellifolia Hooker ex Torrey & A. Gray, Fl. N. Amer. 1: 442. 1840.
Fanleaf or fanfoil or Mount Rainier cinquefoil
Plants ± openly matted; caudex branches short to elongate, ± stout. Stems ascending to erect, (0.3–)1–3 dm, lengths 2 times basal leaves. Basal leaves 2-ranked, ternate, (1–)3–12(–20) cm; stipules: apex rounded; petiole (0.5–)1–15(–18) cm, hairs and glands usually absent; leaflets 3, central widely obovate to flabellate, (0.5–)1–5 × (0.4–)1–3(–3.5) cm, petiolule 0–5(–10) mm, margins flat, not or shallowly lobed (sinuses extending less than 1/2 to midvein), distal 1/2–3/4 usually unevenly incised 1/4–1/2 to midvein, teeth 3–7 per side, ˂often secondarily toothed˃, surfaces similar, green, hairs absent or sparse, rarely common, 0.5–1 mm, glands absent or sparse. Inflorescences 1–6-flowered. Pedicels straight, 0.3–4.5(–5) cm, not much longer in fruit than in flower. Flowers: epicalyx bractlets ˂often toothed or 2-lobed˃, elliptic to oval, 3.5–7 × (1–)1.5–3 mm, margins flat; hypanthium 3–7 mm diam.; sepals 4–8 mm, apex acute to obtuse; petals dark yellow, (5–)6–10(–12) × (3–)5–10 mm; filaments 1.5–3 mm, anthers 0.6–1.5 mm; carpels 20–50, styles filiform, not or slightly papillate-swollen proximally, 1.6–2.5 mm. Achenes 1.2–1.5 mm. 2n = 28.
Flowering summer. Moist to wet or swampy, sometimes dry, stream banks, lakeshores, meadows, in conifer woodlands, subalpine and alpine grassy, rocky slopes, near or above timberline; 1000–3700 m; Alta., B.C.; Calif., Idaho, Mont., Nev., Oreg., Wash., Wyo.
Potentilla flabellifolia is found in the mountains from southern British Columbia, southwestern Alberta, and southwestern Montana to the southern Sierra Nevada of California.