Res. Stud. State Coll. Wash. 2: 125. 1931 (as rupicolum),.
Herbs, perennial, tufted, glabrous. Stems prostrate, becoming erect, branched, bearing rosettes in clusters and secondary shoots in leaf axils. Leaves alternate, (easily detaching and sometimes forming new plants), divergent, slightly upturned, sessile; blade blue-green, purplish, or green, sometimes glaucous, ovate, elliptic-ovate, or lanceolate, subterete, 3.2–6.2 × 1.9–2.9 mm, base not spurred, not scarious, apex obtuse or apparently acute. Flowering shoots erect, simple or branched, ca. 18 cm; leaf blades elliptic to suborbiculate or elliptic-linear, base not spurred; offsets not formed. Inflorescences cymes, 3–22-flowered, 3-branched; branches not or slightly recurved, not forked; bracts narrowly elliptic to linear. Pedicels absent or 3–5 mm. Flowers 5-merous; sepals erect, slightly connate basally, green, lanceolate or lanceolate-oblong, equal, ca. 3 × 1.5 mm, apex obtuse or subacute; petals widely spreading from short, erect base, distinct, deep yellow, elliptic-lanceolate or lanceolate, slightly cucullate, 6.7–8.8 mm, apex obtuse or, rarely, acute with minute mucronate appendage; filaments yellow; anthers yellow; nectar scales yellow, subquadrate. Carpels erect in fruit, connate basally, brown. 2n = 32, 36.
Phenology: Flowering summer.
Elevation: 800-2000 m
The leaves of Sedum rupicola detach very easily and the fallen ones sprout and produce plantlets from their bases. R. T. Clausen (1975) considered S. rupicola to be most closely related to S. lanceolatum. He recognized it as a species because, although it sometimes grows sympatrically with S. lanceolatum, the two do not hybridize, and because S. rupicola flowers a week earlier and grows in soils of higher pH than does S. lanceolatum. The general morphological differences are: in S. rupicolum leaves of sterile shoots are ovate and detach easily, sepals have obtuse apices, petals have minutely mucronate tips (0.1 mm), and nectaries are deep yellow; in S. lanceolatum leaves of sterile shoots are linear-lanceolate and do not detach easily, sepals have acute apices, petal apices are long-acuminate (0.8 mm), and nectaries are pale yellow.