Plants solitary or in clumps, with bulbils on caudices. Leaves basal; petiole flattened, 1-9 cm; blade ovate to elliptic, 2-8 cm, ± fleshy, base attenuate, margins irregularly crenate to serrate, ciliate, surfaces sparsely to ± densely stipitate-glandular and tangled, reddish brown-hairy, adaxially glabrescent. Inflorescences 30+-flowered, (flowers sometimes secund), very open, lax, ± flat-topped thyrses, 6-50 cm, proximally hairy, distally densely purple-tipped stipitate-glandular. Flowers: sepals erect to ascending (even in fruit), ovate to triangular; petals white, not spotted, broadly oblong to elliptic, not or rarely slightly clawed, 3-6 mm, 2+ times as long as sepals; filaments linear, flattened; pistils distinct almost to base; ovary ± superior, (to 1/3 adnate hypanthium). Capsules green to purplish, folliclelike. 2n = 20 (+ 0-6 supernumeraries), 38. Flowering spring. Rocky hillsides, cliffs and shaded rock outcrops, stream banks, wooded slopes; 0-1500 m; Man., N.B., Ont., Que.; Ala., Ark., Conn., D.C., Ga., Ill., Ind., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., W.Va. Also reported for Micranthes virginiensis is 2n = 28; D. E. Soltis (1983) documented zero to six supernumerary chromosomes in this species and speculated that this report may have included eight supernumeraries.
Flowering stems solitary or few together, 1 dm at first flowering, later to 4 dm; basal lvs oblong or ovate, 2-5 cm, entire or serrate, obtuse, cuneately narrowed to a margined petiole; infl branched, at first compact, later lax and open; hypanthium adnate to the base of the carpels; sep spreading or ascending; pet spatulate to obovate, 4-6 mm, white; seeds minutely papillate in longitudinal rows; 2n=20 + several B, 28. Moist or dry open woods and rock-ledges; N.B. to Man., s. to Ga., La., and Okla. Apr., May. (Micranthes v.) Many aberrant forms have been described.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
This species is restricted to the tops and slopes of the bluffs of the Ohio River and nearby. It is local in its distribution but frequent to common where it is found. It is rather common on the top of the bluff of the Ohio River just north of Fredonia in Crawford County. There are specimens from only four counties but I think that it could be found in other counties, especially Floyd, Harrison, and Jefferson Counties and in western Vanderburgh County. Bush (Amer. Midland Nat. 11: 215-220. 1928.) has divided my specimens into two lots. He calls one lot Saxifraga virginiensis and the other Saxifraga pilosa Haworth. I am not recognizing the latter.