1. Leaves (at least the middle and lower ones) with broadly ovate blades and distinct petioles.
2. Sepals mostly 4.5–5 mm long; seeds 0.9–1.3 mm wide, dark brown.
S. media
2. Sepals mostly 3–4 mm long; seeds 0.5–0.9 mm wide, yellowish-brown.
S. pallida
1. Leaves linear to lanceolate, without petioles.
3. Bracts on middle (and lower) portion of inflorescence green, herbaceous; principal leaves ca. 4.5–7 times as long as broad; sepals ca. (1.5–) 2–3.5 mm long, even in fruit.
4. Leaves ± sparsely ciliate, at least toward the base, the principal ones 15–35 (–40) mm long; petals absent or (rarely) nearly equaling the sepals.
S. borealis
4. Leaves completely glabrous, less than 12 (–18) mm long; petals exceeding the sepals.
S. crassifolia
3. Bracts on middle (and usually lower) portion of inflorescence scarious (at most with green midrib); principal leaves often more than 8 times as long as broad; sepals often longer (especially in fruit).
5. Plants short, 3–20 (–25) cm tall, few-flowered (1–5 or rarely 7–10 flowers per stem axis); pedicels ascending; leaves narrowly triangular (tapering evenly from a base up to 2.3 mm broad), ± crowded and strongly ascending.
S. longipes
5. Plants taller, few- to many-flowered; pedicels and branches of inflorescence (at least when mature) strongly divaricate or reflexed; leaves linear to narrowly lanceolate, ± spreading.
6. Median (if not all) leaves broadest at or just above the base; margins of leaves and stems not papillose (rarely ciliate); bracts and usually sepals ciliate; seeds distinctly wrinkled with wavy sculpturing.
S. graminea
6. Median (if not all) leaves linear or slightly broader near the middle; margins of at least upper leaves and angles of the internodes between them finely papillose [20×]; bracts and sepals usually not ciliate; seeds slightly marbled but essentially smooth.
S. longifolia