Hooker’s cinquefoil

Potentilla nivea Linnaeus subsp. hookeriana (Lehmann) Hiitonen; P. nivea var. hookeriana (Lehmann) Th. Wolf

Caudex branches not sheathed with marcescent whole leaves. Stems ascending to nearly erect, (0.3–)0.5–2 dm. Basal leaves usually both ternate and palmate on same plant, rarely subpalmate, 1–9 cm; petiole 0.5–6 cm, long hairs common to abundant, ± appressed to ascending-spreading, (0.5–)1–1.5(–2) mm, usually stiff, rarely weak, verrucose, short-crisped hairs sparse to common, cottony hairs absent, glands ± sparse; leaflets 3–5, proximalmost separated by 0(–1) mm, central oblanceolate to obovate, 0.5–2.5 × 0.4–1.2 cm, petiolules 0–1 mm, distal ± 3/4 of margin incised 1/2–3/4, rarely +, to midvein, teeth 2–6 per side, 1–5 mm, apical tufts 0.5–1 mm, abaxial surfaces grayish white to white, long hairs common to abundant, cottony-crisped hairs usually dense, short hairs and glands absent or obscured, adaxial green to grayish green, long hairs sparse to common, 0.5–1.5 mm, usually stiff, short and/or crisped hairs sparse to common, cottony hairs absent, glands sparse to common. Cauline leaves 1–2. Inflorescences 1–6(–8)-flowered, open, branch angle 20–50°. Pedicels (0.5–)1–2 cm, proximal to 3 cm. Flowers: epicalyx bractlets linear to oblong-lanceolate, 2–3 × 0.7–1.3 mm; hypanthium 3–4 mm diam.; sepals 3–5 mm, apex subacute, glands ± common, not obscured; petals yellow, ± overlapping, 3–6(–7) × 4–5 mm, usually longer than sepals; filaments 0.5–1.5 mm, anthers 0.3–0.5 mm; carpels 30–50, styles 0.8–1.2 mm. Achenes 1–1.3 mm.

Flowering (spring–)summer. Alpine ridges, fellfields, scree slopes, rocky canyons; 1400–3900 m; Alta., B.C.; Colo., Idaho, Mont., Nev., Utah, Wyo.

As here defined, Potentilla hookeriana consists of primarily alpine plants from the Rocky Mountains and adjacent desert mountains that share many of the same characters with P. rubricaulis but are smaller overall. Arctic plants previously included in P. hookeriana are now assigned to P. arenosa (J. Soják 1986; B. Ertter et al. 2013).