Potentilla sect. Aureae |
Potentilla nana |
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arctic cinquefoil, dwarf cinquefoil |
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Habit | 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). | Plants densely tufted; caudex branches short, slender to ± stout, diam. 0.5–1 cm, including old leaf bases. | ||||||||||||||||||||||||||||||||||||||||||||||||
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. |
ascending to erect, 0.1–0.5(–0.7) dm, lengths 1–2 times basal leaves. |
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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. |
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Basal leaves | not in ranks, ternate, 1–5 cm; stipules: apex acute; petiole 0.5–3.5 cm, long hairs sparse to abundant, ascending to spreading, 0.5–2 mm, ± soft, glands sparse to common; leaflets 3, central obovate, 0.5–2 × 0.5–1 cm, petiolule 0–1 mm, margins revolute, not lobed, distal 1/2–2/3 evenly incised ± 1/2 to midvein, teeth 3–4(–6) per side, surfaces ± similar, green (paler abaxially), hairs sparse to abundant, 0.8–1.2 mm, glands sparse to common. |
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Inflorescences | 1–6(–12)-flowered, ± cymose, ± to very open, or solitary flowers. |
1(–2)-flowered. |
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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). |
straight, 0.2–1.5 cm in flower, to 5 cm in fruit. |
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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. |
epicalyx bractlets oblong or ovate, 2.5–5 × 1.5–3.5 mm, margins revolute; hypanthium 3–3.5 mm diam.; sepals 2.5–5 mm, apex ± acute; petals pale yellow, 4–8 × 4–6 mm; filaments 1.2–2 mm, anthers 0.3–0.4 mm; carpels 40–50, styles ± columnar, not or scarcely papillate-swollen proximally, 0.8–1.2 mm. |
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Achenes | ± smooth. |
1.4–1.6 mm. |
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Potentilla sect. Aureae |
Potentilla nana |
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Phenology | Flowering summer. | |||||||||||||||||||||||||||||||||||||||||||||||||
Habitat | Alpine and coastal Dryas-Salix-Empetrum heaths, gravelly slopes, ridge crests, fellfields, scree and talus | |||||||||||||||||||||||||||||||||||||||||||||||||
Elevation | 100–1100 m (300–3600 ft) | |||||||||||||||||||||||||||||||||||||||||||||||||
Distribution | North America; Eurasia [Reportedly introduced in s Australia] |
AK; BC
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Discussion | Species ca. 30 (10 in the flora). 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. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Potentilla nana has most often been considered a race of P. hyparctica or as the priority name for P. hyparctica. As now defined, P. nana occurs in an arc across southern Alaska, from the Aleutian and Pribilof islands to the Alaskan panhandle and adjacent British Columbia. T. Wolf (1908) treated it as a dwarf form of P. fragiformis; J. Soják (1996) interpreted P. nana as a hybrid species originating from cross(es) between P. fragiformis and P. hyparctica. Although the hybrid hypothesis has morphologic support, P. nana has a unique combination of morphologic features and has a distinct range from both P. fragiformis and P. hyparctica. The species are also ecologically segregated: P. nana is a coastal heath and gravel slope species, like P. hyparctica; P. fragiformis is strictly maritime coastal. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 9, p. 188. | FNA vol. 9, p. 192. | ||||||||||||||||||||||||||||||||||||||||||||||||
Parent taxa | ||||||||||||||||||||||||||||||||||||||||||||||||||
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Synonyms | P. unranked Aureae, P. ser., P. section Frigidae | P. emarginata subsp. nana | ||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | (Rydberg) Juzepczuk: in V. L. Komarov et al., Fl. URSS 10: 197. (1941) | D. F. K. Schlechtendal: Ges. Naturf. Freunde Berlin Mag. Neuesten Entdeck. Gesammten Naturk. 7: 296. (1816) | ||||||||||||||||||||||||||||||||||||||||||||||||
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