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FNA | Family List | FNA Vol. 9 | Rosaceae | Potentilla

8r. Potentilla Linnaeus sect. Aureae (Rydberg) Juzepczuk in V. L. Komarov et al., Fl. URSS. 10: 197. 1941.

Reidar Elven, Barbara Ertter, David F. Murray, James L. Reveal

Potentilla [unranked] Aureae Rydberg, Bull. Torrey Bot. Club 23: 394. 1896; Potentilla ser. Aureae (Rydberg) T. T. Yü & C. L. Li; Potentilla sect. Frigidae (Rydberg) O. Stevens

Perennials, tufted to cushion-forming or matted, rarely rosetted, not stoloniferous (except sometimes P. verna); taproots not fleshy-thickened; vestiture primarily of straight hairs, not differentiated into long and short, glands absent or sparse to abundant, sometimes red (P. hyparctica). Stems usually ascending to erect, sometimes prostrate to decumbent or spreading, not flagelliform, not rooting at nodes (except P. verna), lateral to persistent basal rosettes, 0.1–2(–3) dm, lengths 1–3(–4) times basal leaves. Leaves: basal sometimes 2-ranked; cauline 0–2(–3); primary leaves ternate or palmate, (0.5–)1–12(–20) cm; petiole: long hairs absent or spreading to ascending, weak to ± stiff, glands usually absent or sparse, sometimes abundant; leaflets 3–7, at tip of leaf axis, overlapping or not, broadly oblanceolate or obtriangular to flabellate, margins flat to revolute, distal 1/4–3/4+ evenly to unevenly incised 1/4–1/2 to midvein, ˂sometimes 3–5-lobed 1/2–3/4 to midvein as well˃, primary teeth (1–)2–5(–7) per side ˂or per lobe˃, surfaces ± similar, abaxial pale to dark green, rarely grayish, brownish, or reddish, cottony hairs absent, adaxial green to dark green, rarely brownish or reddish, sometimes ± glaucous (P. grayi), long hairs (if present) soft to weak, sometimes stiff. Inflorescences 1–6(–12)-flowered, ± cymose, ± to very open, or solitary flowers. Pedicels usually straight in fruit (often recurved in P. verna), (0–)0.2–3(–9) cm, proximal usually not much longer than distal (sometimes longer in fruit). Flowers 5-merous; hypanthium 2–7 mm diam.; petals pale to dark yellow, mostly ± obcordate (to orbiculate in P. elegans), (2–)3–10(–12) mm, usually longer than sepals, apex usually ± retuse; stamens ca. 20; styles subapical, columnar, filiform, or tapered, not, scarcely, or ± papillate-swollen in proximal 1/5–1/2, 0.8–2.5 mm. Achenes ± smooth.

Species ca. 30 (10 in the flora): North America, Eurasia; reportedly introduced in s Australia.

The circumscription of sect. Aureae used here largely follows that of B. C. Johnston (1985), except that Potentilla sierrae-blancae is placed in sect. Concinnae and P. rubella and P. stipularis are in sect. Chrysanthae. Other treatments (for example, P. A. Rydberg 1908d; T. Wolf 1908) split the species included here in two groups and/or recombine them with species in other sections, notably sect. Ranunculoides (Th. Wolf) Juzepczuk.

Since Potentilla glaucophylla (sect. Graciles) and P. cottamii (sect. Subviscosae) are sometimes identified as members of sect. Aureae, they are included herein and key out in the third and twelfth couplets, respectively.

1 Basal leaflets (3–)4–7   (2)
+ Basal leaflets 3   (4)
2 (1) Basal leaves not in ranks; stems usually prostrate to decumbent, rarely weakly erect; caudex branches elongate and slender; pedicels often recurved; introduced.   62 Potentilla verna
+ Basal leaves 2-ranked; stems ascending to erect; caudex branches usually short and stout, sometimes elongate and slender; pedicels straight; native   (3)
3 (2) Leaves glaucous, ± blue-green; styles 1.5–2.5(–3) mm; sepals: apex acute to short acuminate; w North America, Greenland.   23 Potentilla glaucophylla (sect. Graciles) (in part)
+ Leaves not glaucous, green; styles 1–1.6 mm; sepals: apex broadly acute; ne Canada, Greenland.   63 Potentilla crantzii (in part)
4 (1) Central leaflets deeply 3–5-lobed (sinuses extending 1/2 to nearly to midvein), lobes unevenly incised 1/4–1/2 to midvein, teeth (1–)2–5 per lobe, glands sparse to abundant   (5)
+ Central leaflets not or shallowly lobed (sinuses extending less than 1/2 to midvein), evenly or unevenly incised 1/4–1/2 to midvein, teeth 2–7 per side, glands absent or sparse to common   (6)
5 (4) Styles 1.3–2 mm; stems 0.3–2 dm; sepals 3–5 mm; nw California.   66 Potentilla cristae
+ Styles 0.7–0.9 mm; stems 0.1–0.5 dm; sepals 2.2–2.5 mm; arctic.   71 Potentilla elegans
6 (4) Leaflet and epicalyx bractlet margins revolute; British Columbia, Alaska   (7)
+ Leaflet and epicalyx bractlet margins flat, sometimes slightly or ± revolute; North America   (8)
7 (6) Petals 9–12 mm; caudex branches stout (diam. 1–2 cm, including old leaf-bases); filaments (2–)2.8–3.2 mm; styles 1.7–2 mm; 0–10 m.   67 Potentilla fragiformis
+ Petals 4–8 mm; caudex branches slender to ± stout (diam. 0.5–1 cm, including old leaf-bases); filaments 1.2–2 mm; styles 0.8–1.2 mm; 100–1100 m.   68 Potentilla nana
8 (6) Styles 1–2.5 mm; filaments 1–3 mm   (9)
+ Styles 0.6–1 mm; filaments 0.5–1(–1.5) mm   (11)
9 (8) Leaflet margins usually unevenly incised, teeth 3–7 per side, often secondarily toothed.   64 Potentilla flabellifolia
+ Leaflet margins evenly incised, teeth (2–)3–4(–5) per side, not secondarily toothed   (10)
10 (9) Petioles: long hairs 1–2.5 mm; central leaflets: petiolules 0–1 mm; Greenland, ne Canada.   63 Potentilla crantzii (in part)
+ Petioles: long hairs 0.5–1 mm; central leaflets: petiolules (1–)3–10 mm; California.   65 Potentilla grayi
11 (8) Epicalyx bractlets 3.5–7 mm; petals 4–9 mm.   69 Potentilla hyparctica
+ Epicalyx bractlets (1.8–)2–2.5(–3) mm; petals 2–3 mm   (12)
12 (11) Epicalyx bractlets 1/2–3/4 as long as sepals; inflorescences 1–4-flowered; Great Basin.   60 Potentilla cottamii (sect. Subviscosae) (in part)
+ Epicalyx bractlets ± equal to sepals; inflorescences 1(–2)-flowered; New England.   70 Potentilla robbinsiana


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