Novosti Sist. Vyssh. Rast. 6: 309. 1970.
Plants sometimes canescent basally; caudex branched. Stems: several from base, unbranched, (0.3–)0.5–1.4(–2) dm, trichomes simple, 0.3–1 mm, mixed with smaller, dendritic ones, (sometimes simple ones absent). Basal leaves: petiole 0.7–3(–4) cm, often ciliate, trichomes simple; blade usually linear to oblanceolate or spatulate, rarely obovate, (0.5–)0.8–2.2(–3.5) cm × 0.7–5(–7) mm, margins usually entire, rarely apically 3 or 5-toothed or -lobed, apex obtuse to rounded, (surfaces densely tomentose, grayish, trichomes mostly dendritic, mixed with fewer, simple ones, to 1 mm). Cauline leaves shortly petiolate; blade similar to basal, smaller distally, margins usually entire, rarely lobed. Racemes elongated in fruit. Fruiting pedicels divaricate to ascending, (forming 30–70˚ angle), proximalmost bracteate, 4–12 mm, pubescent, trichomes simple mixed with smaller, dendritic ones. Flowers: sepals 2.5–3.5 mm; petals white or creamy white, suborbicular to obovate, 4–6 × 2–3(–4) mm, narrowed to claw, 1–2(–3) mm, apex rounded; anthers oblong, 0.5–0.7 mm. Fruits divaricate to ascending, ellipsoid to oblong, subterete or slightly 4-angled, 6–10 × 1.5–2.5 mm, base and apex cuneate; valves each with prominent midvein; ovules 4–8 per ovary; style 0.1–0.5 mm. Seeds 1.5–2 × 0.9–1.2 mm. 2n = 12, 22, 24.
Phenology: Flowering Jun–Jul.
Habitat: Scree, dry gravelly slopes, sandstone shale-scree, fellfields, gravel beaches and benches, slides, alpine ridges, rock crevices and outcrops, sedge tundra, Dryas heath meadows, dry slopes, tundra slopes, conglomerate outcrops, marshes, sedge meadows, windswept sandstone ridges
Elevation: 0-1700 m
Alaska, e Asia (Russian Far East).
As delimited here, Smelowskia porsildii is taken in the broad sense to include plants recognized by W. H. Drury Jr. and R. C. Rollins (1952) and Rollins (1993) as S. calycina var. integrifolia. The latter was raised by Velichkin to species rank, named as S. spathulatifolia because of the earlier-published S. integrifolia Bunge. Leaf shape and pedicel orientation, used by those authors to distinguish the two taxa, vary continuously. The species is also highly variable in the relative occurrence of simple versus dendritic trichomes and leaf margins. Although I. A. Al-Shehbaz and S. I. Warwick (2006) reduced S. spathulatifolia to synonymy of S. porsildii, the latter most likely represents a complex in which S. media might be involved. Conflicting chromosome numbers (e.g., 2n = 12, 18, 22, 24, 32) have been reported for this complex (Warwick and Al-Shehbaz 2006), and detailed cytological and molecular studies are needed to resolve the taxa involved. The complex involves diploid and tetraploid populations based on x = 6; the counts of 2n = 18 and 32 most likely reflect misidentifications.