White Mountains cinquefoil, Robbins’s cinquefoil

Potentilla minima Haller f. var. robbinsiana Lehmann, Revis. Potentill., 159. 1856; P. hyparctica Malte subsp. robbinsiana (Lehmann) Á. Löve & D. Löve

Plants tufted to densely matted; caudex branches short, ± slender, ˂often embedded in old leaf bases˃. Stems spreading to erect, 0.1–0.4 dm, lengths 1–2 times basal leaves. Basal leaves not in ranks, ternate, 1–2 cm; stipules: apex broadly acute; petiole 0.7–3 cm, long hairs sparse to abundant, spreading to subappresed, 0.2–2 mm, weak, glands sparse to common; leaflets 3, central obovate, 0.5–1.3 × 0.2–1 cm, petiolule 0–1 mm, margins flat to ± revolute, not lobed, distal ± 2/3 evenly incised ± 1/2 to midvein, teeth 2–4(–5) per side, surfaces similar, green, hairs ± abundant (or nearly absent adaxially), 0.5–1 mm, glands sparse to common. Inflorescences 1(–2)-flowered. Pedicels straight, 0.5–3 cm, not much longer in fruit than in flower. Flowers: epicalyx bractlets oblong to elliptic, (1.8–)2–2.5(–3) × 0.7–1.2(–1.4) mm, ˂± equal to sepals˃, margins flat to ± revolute; hypanthium (4–)5–7 mm diam.; sepals (1.8–)2–2.5(–3) mm, apex broadly acute; petals yellow, 2–3 × 2–3 mm; filaments 0.5–1 mm, anthers 0.4–0.6 mm; carpels 20–30, styles columnar-tapered, sometimes ± papillate-swollen in proximal 1/3–1/2, 0.8–1 mm. Achenes 1–1.3 mm. 2n = 49.

Flowering summer. Moist rocky slopes and flats, in montane tundra; of conservation concern; 1400–1600 m; N.H., Vt.

Potentilla robbinsiana is known only from two sites in the White Mountains, Monroe County, New Hampshire, and is reported in Vermont. Additional populations have been established nearby as a result of transplant efforts. Listed in 1980 as a federally endangered species, an intense recovery program resulted in the species being delisted in 2002.

Some early specimens were distributed as Potentilla frigida Villars, a similar European species.

Selected References Cogbill, C. V. 1968. The interplay of botanists and Potentilla robbinsiana: Discovery, systematics, collection, and stewardship of a rare species. Rhodora 95: 52–75. Graber, R. E. 1980. The life history and ecology of Potentilla robbinsiana. Rhodora 82: 131–140. Graber, R. E. and L. G. Brewer. 1985. Changes in the population of the rare and endangered plant Potentilla robbinsiana Oakes during the period 1973 to 1983. Rhodora 87: 449–457. Steele, F. L. 1964. Potentilla robbinsiana in the White Mountains of New Hampshire. Rhodora 66: 408–411.