27. Potentilla pulcherrima Lehmann, Nov. Stirp. Pug. 2: 10. 1830.
Potentilla filipes Rydberg; P. gracilis Douglas ex Hooker var. filipes (Rydberg) B. Boivin; P. gracilis var. pulcherrima (Lehmann) Fernald; P. pulcherrima var. condensata Th. Wolf; P. pulcherrima var. filipes (Rydberg) Th. Wolf; P. pulcherrima var. wardii (Greene) Soják
Glands usually conspicuous, red-tipped (palmate-leaved plants), sometimes absent or inconspicuous, colorless (subpalmate-leaved plants). Stems ascending to erect, (1.5–)3–6(–8) dm. Basal leaves sometimes 2-ranked, palmate to subpalmate, 3–25(–35) cm; petiole 1–20(–30) cm, long hairs sparse to abundant, appressed to spreading, 2–3 mm, weak to stiff, short hairs usually absent, crisped hairs absent or sparse, cottony hairs usually absent, glands sparse to abundant; leaflets 5–7, at tip or on distal 1/10 of leaf axis, separate to slightly overlapping, largest ones ± oblanceolate, 1–6(–9) × 1–4 cm, margins flat, distal 2/3 to nearly whole length evenly incised 1/4–1/2 to midvein, undivided medial blade 6–15 mm wide, teeth 6–12 per side, ± broadly lanceolate, 1–5 mm, surfaces usually strongly dissimilar, abaxial grayish to white, long hairs sparse to common (mostly on veins), short hairs absent, cottony or crisped-cottony hairs abundant to dense, glands usually ± abundant (at least on veins), adaxial green, rarely grayish green, not glaucous, long hairs sparse to common, short, crisped, and cottony hairs usually absent, glands usually sparse to abundant. Cauline leaves 1–3. Inflorescences (4–)10–50(–60)-flowered. Pedicels 0.5–3(–4.5) cm. Flowers: epicalyx bractlets narrowly lanceolate to narrowly elliptic, 3–5(–6) × 0.8–2 mm, hairs sparse to common, ± appressed to spreading, glands absent or sparse to abundant; hypanthium (3–)4–6 mm diam.; sepals 4–8(–9) mm, apex acuminate; petals 6–9(–11) × 6–13 mm; filaments 1–3.5 mm, anthers 0.8–1.1 mm; carpels 20–40, styles filiform to tapering above papillate-swollen base, (1–)1.5–2 mm. Achenes 1.1–1.5(–1.6) mm. 2n = 70, 71, 108.
Flowering summer. Dry meadows in grasslands, sagebrush, scrub oak, aspen and conifer woodlands; (300–)800–3600 m; Alta., B.C., Man., Ont., Que., Sask.; Ariz., Calif., Colo., Conn., Idaho, Mont., Nev., N.Mex., N.Dak., S.Dak., Utah, Wyo.
Potentilla pulcherrima is here retained provisionally in the broad sense, encompassing intergrades between morphological extremes. The most distinctive extreme has strictly palmate leaves and conspicuous red-tipped glands. Eglandular hairs are relatively sparse and spreading on epicalyx bractlets and abaxial leaflet veins, such that the veins tend to contrast with the cottony white abaxial surface. At the other extreme are plants with subpalmate leaves, no or inconspicuous glands, and densely strigose abaxial leaflet veins. The former is understood to be the core species, towards which the description is accordingly weighted. The latter in turn represents introgression with P. hippiana (sect. Leucophyllae) or other species. The subpalmate extreme includes the lectotype of P. pulcherrima (designated by J. Soják 1996), so if a narrower circumscription of the species is adopted then either P. filipes would become the accepted name of the core species or predominant current usage of P. pulcherrima would have to be conserved by designating a different type.
By whatever circumscription, Potentilla pulcherrima is one of the more common members of sect. Graciles in the Rocky Mountains, extending east into the northern prairies. The species grows mainly in the mountains from southeastern British Columbia and southern Alberta to northern and eastern Arizona and southern New Mexico. The native range extends at least to Manitoba and North Dakota, with outlying populations in the Black Hills of South Dakota. Populations are also scattered in the mountains of eastern Nevada and disjunctly in the White Mountains of California. Adventive occurrences in fields and disturbed sites are reported from as far east as Connecticut; see discussion of P. gracilis for reports from New Hampshire. All known specimens from Minnesota and Oregon have been reidentified as particularly hairy variants of P. gracilis in the broad sense; reports from Washington are suspect.
Potentilla pulcherrima has often been treated as a variety of P. gracilis, sometimes with the filipes extreme included in var. gracilis (B. Boivin 1967–1979). The current decision to treat P. pulcherrima as a species is in part because it has a monsoonal Rocky Mountain rather than a Pacific Northwest center of distribution.
Plants combining the vestiture of Potentilla pulcherrima, including abundant glandularity, with subpalmate leaves approaching P. hippiana (leaflets on about one-fifth of leaf axis) have been named P. gracilis var. hippianoides S. L. Welsh & N. D. Atwood.