Muir’s ivesia, granite mousetail

Potentilla muirii (A. Gray) Greene

Plants silvery, usually ± rosetted; taproot stout, sometimes fleshy. Stems usually ± erect, sometimes nearly prostrate, 0.5–1.5(–2) dm. Basal leaves very tightly cylindric (mousetail-like, with individual leaflets scarcely distinguishable), 2–5(–10) cm; sheathing base densely strigose abaxially; petiole 0.2–0.8(–1) cm, hairs 0.5–1.5 mm; leaflets 25–40 per side, 0.4–1 mm, densely sericeous, glands obscured, lobes 2–5, obovate or oval to orbiculate, apex not setose. Cauline leaves (0–)1–2, paired if 2. Inflorescences 10–30-flowered, 1–2(–3.5) cm diam.; glomerules usually 1. Pedicels 0.3–2(–3.5) mm. Flowers 5–6 mm diam.; epicalyx bractlets oblong to obovate, 0.5–1 mm; hypanthium shallowly cupulate, 0.5–1(–1.5) × 1.5–2.5 mm; sepals (1–)1.5–2.5 mm, acute; petals yellow, linear to oblanceolate or narrowly oblong, 1–2 mm; stamens 5, filaments 0.3–0.6 mm, anthers yellow, 0.4–0.6 mm; carpels 1–4, styles 0.7–1.2 mm. Achenes grayish brown, mottled with red, 1.6–2 mm.

Flowering summer. Dry rocky slopes, fellfields, mostly in alpine conifer woodlands and tundra; 2900–4000 m; Calif.

Ivesia muirii is known from alpine areas in the Sierra Nevada. It is one of the more distinctive species of the genus, in its silvery mousetail-like leaves and usually tightly capitate inflorescences. Putative hybrids are known with I. lycopodioides (D. D. Keck 1938) and I. pygmaea (Center Basin area of Tulare County).