Barbara Ertter, James L. Reveal

Potentilla [unranked] Rubrae Rydberg in N. L. Britton et al., N. Amer. Fl. 22(4): 293, 323. 1906; Potentilla sect. Haematochrus (Rydberg) Schiman-Czeika; Potentilla [unranked] Haematochrus Rydberg; Potentilla sect. Haematochrus (Rydberg) B. C. Johnston

Perennials, ± tufted, not stoloniferous; taproots not fleshy-thickened; vestiture of long, short, crisped, and/or cottony hairs, glands sparse to abundant, rarely reddish. Stems ascending to nearly erect, not flagelliform, not rooting at nodes, lateral to persistent basal rosettes, (2–)3–7(–10) dm, lengths (2–)3–5 times basal leaves. Leaves: basal not 2-ranked; cauline 1–3; primary leaves palmate to ± subpalmate, (2–)4–15(–30) cm; petiole: long hairs spreading to weakly appressed, weak to ± stiff, glands sparse to abundant, rarely absent; leaflets 5–7, on tip or less than distal 1/10 of leaf axis, ± overlapping or not, oblanceolate or oblong to elliptic or obovate, margins flat, distal 1/2 to whole length evenly incised 1/5–1/4 or less to midvein, teeth (0–)4–15(–19) per side, surfaces similar or slightly to strongly dissimilar, abaxial green to white, cottony hairs absent or sparse to dense, adaxial green, not glaucous, long hairs weak to stiff. Inflorescences (4–)10–40(–70)-flowered, cymose, open. Pedicels straight in fruit, 0.3–4 cm, proximal ± longer than distal. Flowers 5-merous; hypanthium 4–6 mm diam.; petals dark reddish to reddish orange, ± obcordate, (3.5–)5–10 mm, equal to or longer than sepals, apex retuse; stamens 20–30; styles subapical, tapered-filiform, papillate-swollen in proximal 1/5, 2–3.5 mm or less. Achenes ± rugose.

Species 9 (2 in the flora): sw United States, Mexico, Asia.

Red petals distinguish species of sect. Rubrae from the remaining species assigned here to Potentilla. Most species in the section occur in Mexico. As traditionally defined, sect. Rubrae also includes the southeastern Asian species P. atrosanguinea Loddiges, G. Loddiges & W. Loddiges (3 leaflets), P. argyrophylla Wallich ex Lehmann (3 leaflets), and P. nepalensis Hooker (5 leaflets). The first is available in the horticultural trade and was reported in a strawberry field in New Brunswick, Canada (B. Boivin 1966b; H. J. Scoggan 1978–1979, part 3); it did not become naturalized. The name P. argyrophylla var. atrosanguinea (Loddiges, G. Loddiges & W. Loddiges) Hooker f., used in the Flora of China (Li C.-L. et al. 2003c) is incorrect; P. argyophylla (1831) is a name later than P. atrosanguinea (1823).