1a. Petrorhagia saxifraga (Linnaeus) Link var. saxifraga
Plants perennial with woody bases. Stems ascending to erect, much-branched, 5-40 cm; in-ternodes glabrous distally, scabrous proximally. Leaves: sheath 1 mm or less, ± as long as wide; blade 1-veined, linear, 5-20 (-30) mm, margins basally ciliate. Inflorescences lax cymes or flowers solitary; involucel bracteoles enclosing to 2 of calyx, narrowly ovate, scarious, apex acute. Pedicels 5-20 mm. Flowers: sepals 4-6 mm; petals white to pink, primary veins 3, veins often dark pink near base of blade, apex obcordate. Seeds shield-shaped, 0.8-1.3 mm, tuberculate. 2n = 30, 60 (both Europe).
Flowering summer-early autumn. Lawns, roadsides, sandy waste areas; 0-1100 m; introduced; B.C., Ont.; Idaho, Ill., Maine, Mass., Mich., Minn., N.Y., Ohio, Pa., S.Dak., Va., Wis.; c, s Europe; sw Asia; introduced in Europe (Great Britain, Sweden).