1. Sibbaldiopsis tridentata (Aiton) Rydberg, Monogr. N. Amer. Potentilleae. 187. 1898.
Three-toothed cinquefoil, potentille tridentée
Potentilla tridentata Aiton, Hort. Kew. 2: 216, plate 9. 1789; Sibbaldia tridentata (Aiton) Paule & Soják
Leaves: stipules 3–6 mm, margins villous-ciliate; petiole slender, (0.2–)0.5–6(–8) cm; leaflets dark green abaxially, light green adaxially, (0.5–)1–3(–4) × 0.4–1.5(–1.8) cm. Pedicels 2–35 mm, glabrous. Flowers: epicalyx bractlets lanceolate, 1–2 mm; sepals 2–3 mm, hirsute, glandular; petals white, sometimes pink-tinged, (4–)5–8[–11] mm; anthers reddish, 0.3–0.6 mm; styles 1–2.5(–3) mm. Achenes dark brown. 2n = 14, 28.
Flowering summer. Dry rocky to gravelly shores or maritime habitats, rocky outcrops, montane balds and promontories in mixed conifer-hardwood woodlands, dry meadows of montane conifer communities, alpine tundra, often in acidic soil; 0–1900 m; of conservation concern; Greenland; St. Pierre and Miquelon; Alta., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask.; Conn., Ga., Ill., Iowa, Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.C., N.Dak., Pa., R.I., Tenn., Vt., Va., W.Va., Wis.
Sibbaldiopsis tridentata is uncommon to rare through most of its southern range from Connecticut south to Georgia and west to Iowa, Tennessee, and North Dakota. It is more common in Canada and around the Great Lakes. The inclusion of Scotland in the distribution of the species by P. A. Rydberg (1898) is erroneous (T. Wolf 1908).