Barbara Ertter

Potentilla [unranked] Concinnae Rydberg, Bull. Torrey Bot. Club 23: 431. 1896

Perennials, usually rosetted to tufted, not stoloniferous; taproots sometimes thick, not fleshy; vestiture primarily of long and/or cottony hairs (and crisped hairs in inflorescence), glands absent or sparse to abundant, rarely reddish. Stems prostrate to ± decumbent, not flagelliform, not rooting at nodes, lateral to persistent basal rosettes, 0.2–1.5(–2.7) dm, lengths 1/2–3(–4) times basal leaves. Leaves: basal not in ranks; cauline 0–2; primary leaves palmate to subpalmate, sometimes subpinnate to pinnate (distal leaflets sometimes confluent), 1.5–12(–15) cm; petiole: long hairs ± appressed to ascending, stiff to weak, glands absent or sparse or obscured, rarely abundant; leaflets (3–)5–9(–11), at tip or to distal 3/4+ of leaf axis, separate to strongly overlapping, narrowly oblanceolate or cuneate to obovate, margins flat, less than distal 1/5 to whole length evenly, sometimes unevenly, incised 1/4–3/4+ to midvein, sometimes medially cleft as well, rarely entire, teeth (0–)1–5(–10) per side, surfaces similar to strongly dissimilar, abaxial green to white, cottony hairs absent or sparse to dense, adaxial green to grayish, not glaucous, long hairs usually stiff, rarely weak. Inflorescences (1–)2–12(–15)-flowered, usually ± cymose, open, sometimes racemiform when prostrate. Pedicels often recurved in fruit, 0.7–3(–4.5) cm, proximal usually not much longer than distal. Flowers 5-merous; hypanthium 2.5–6 mm diam.; petals yellow, ± obcordate, (2.5–)3.5–7(–9) mm, longer than sepals, apex usually ± retuse; stamens ca. 20; styles subapical, filiform to filiform-tapered, not papillate-swollen or in proximal 1/5, (1–)1.5–3 mm. Achenes smooth to ± rugose.

Species ca. 10 (8 in the flora): w North America, n Mexico.

Section Concinnae, as here defined, accommodates a cluster of species that occur from the western Great Plains to California and to the mountains of northern Mexico. Stems are commonly prostrate or nearly so and are sometimes shorter than the basal leaves; pedicels tend to become recurved in fruit. Inflorescences often have abundant reddish papillae at the bases of hairs on hypanthia, epicalyx bractlets, and sepals. Leaves are most commonly palmate to subpalmate (except for Potentilla angelliae, P. macounii, and P. morefieldii), most often sparsely to densely cottony abaxially (except for P. multisecta, P. johnstonii, and P. sierrae-blancae), and strigose adaxially with stiff, verrucose hairs, which are sometimes yellowish. Petioles are usually sparsely to densely strigose with stiff, verrucose hairs.

Both P. A. Rydberg (1908d) and B. C. Johnston (1980, 1985) restricted sect. Concinnae to species with palmate, abaxially cottony leaves. Given the unifying or transitional nature of other morphologic and biogeographic features, the circumscription presented here seems more justified.

P. A. Rydberg (1908d) included New Mexico in the distribution of the otherwise Mexican species Potentilla oblanceolata Rydberg, repeated in subsequent floras (I. Tidestrom and T. Kittell 1941; W. C. Martin and C. R. Hutchins 1980). No specimens are currently known to confirm the presence of this species north of Mexico, and it is excluded here.

Since Potentilla breweri (sect. Multijugae) is sometimes identified as a member of sect. Concinnae, it is included herein and keys out in the ninth couplet.