Tweedy’s ivesia

Potentilla tweedyi (Rydberg) J. T. Howell

Plants green, ± rosetted to tufted; taproot stout, not fleshy. Stems ascending to erect, 0.4–2(–3.5) dm. Basal leaves loosely cylindric, (3–)4–12(–17) cm; sheathing base glabrous abaxially; petiole 0.5–7 cm, hairs 1–1.5 mm; leaflets 10–16 per side, 4–7(–10) mm, glabrous or sparsely hirsute, glandular-puberulent or -pubescent, lobes (2–)5–15, linear to narrowly oblanceolate, apex not setose. Cauline leaves (0–)1–2, not paired. Inflorescences (5–)10–25(–35)-flowered, (1–)1.5–3(–4.5) cm diam.; glomerules 1–few. Pedicels 1–3(–5) mm. Flowers 9–12 mm diam.; epicalyx bractlets linear, 1–2 mm; hypanthium shallowly campanulate, 1–1.5 × 2–4(–5.5) mm; sepals 2–3.5 mm, acute; petals golden yellow, broadly elliptic to spatulate, 2.5–3.3 mm; stamens 5, filaments 1–1.7 mm, anthers yellow, 0.5–0.8 mm; carpels (2–)4–6(–9), styles 2–3 mm. Achenes olive green, 1.8–2 mm.

Flowering summer. Dry, gravelly to rocky flats, slopes, alpine ridges, often on serpentine, in subalpine conifer woodlands; of conservation concern; 1600–2300 m; Idaho, Mont., Wash.

Ivesia tweedyi is found from the Cascade Range in Washington to Boundary and Shoshone counties in Idaho, barely entering Montana in Mineral County.