Flagstaff cinquefoil

Potentilla thurberi A. Gray var. sanguinea (Rydberg) Kearney & Peebles

Stems 3–7(–10) dm. Basal leaves ± subpalmate, sometimes palmate, (4–)6–15(–21) cm; petiole (2–)4–10(–15) cm, long hairs sparse to abundant, spreading to weakly appressed, 0.5–2(–3) mm, weak to ± stiff, glands sparse to abundant; leaflets (5–)7, on less than distal 1/10 (1–5[–10] mm) of leaf axis, central one 1–6(–7) × 1–2(–3) cm, petiolules 0(–6) mm, distal 1/2–3/4 (sometimes nearly whole), margin incised 1/5 or less to midvein, teeth 4–10(–15) per side, 1–2(–3) mm, teeth apex ± obtuse, surfaces ± similar, abaxial green, straight hairs sparse to abundant, especially on veins, 0.5–1.5 mm, cottony hairs absent, glands ± sparse or absent, adaxial slightly paler green, hairs shorter and sparser. Cauline leaves: stipules usually entire. Inflorescences (4–)8–40(–70)-flowered. Pedicels 0.3–2 cm. Flowers: epicalyx bractlets lanceolate-elliptic, 3.5–8 × 1–1.5(–2) mm; sepals 4–8(–10) mm, apex acuminate; petals dark reddish proximally, reddish orange distally, (3.5–)5–9 × 5–10 mm; filaments 1.5–2.5 mm, anthers 0.8 mm; carpels 30–40, styles 2–3 mm. Achenes 1.5–2 mm, lightly rugose.

Flowering summer. Moist forest settings in oak and conifer woodlands; of conservation concern; 2100–2200 m; Ariz.

Potentilla sanguinea is known only from south and east of Flagstaff, Coconino County. The species may be a hybrid between P. thurberi var. thurberi and P. hippiana or another member of sect. Leucophyllae that occurs sympatrically.