| | 1. Annual, from slender taproot |
| |
| | 2. Leaves crowded near base, blade generally linear-lanceolate (to ovate); internodes glabrous or hairs scattered; bracts scarious |
| S. nitens |
| | 2' Leaves ± evenly spaced, blade ± ovate; internodes with line of wavy hairs; bracts leafy |
| |
| | 3. Sepals 3–4.5 mm, < 6 mm in fruit; petals generally present; seeds 0.9–1.3 mm, dark reddish or purplish brown |
| S. media |
| | 3' Sepals 2–3 mm, < 4 mm in fruit; petals 0; seeds 0.7–0.8 mm, light reddish brown |
| S. pallida |
| | 1' Perennial, from slender, white rhizomes |
| |
| | 4. Plant covered (except ± leaves) with long wavy hairs — coastal marshes and bluffs, North Coast, Central Coast |
| S. littoralis |
| | 4' Plant glabrous or hairs restricted to stem or leaf margin |
| |
| |
| | 6. Inflorescence ± narrow; pedicels ascending to erect; flower generally 1–7 |
| S. longipes var. longipes |
| | 6' Inflorescence open, branches widely spreading; pedicels spreading or reflexed; flower generally many |
| |
| | 7. Sepals 4–5.5 mm, margin of some densely ciliate; inflorescence terminal; seeds with prominent, elongate tubercles; leaf margin ± smooth, shiny |
| S. graminea |
| | 7' Sepals 3–4 mm, margin ± glabrous; inflorescence lateral; seeds minutely roughened; leaf margin papillate (at 20× magnification), dull |
| S. longifolia |
| | 5' Petals < 0.8 × sepals or 0 |
| |
| | 8. Flowers many (except in alpine), in umbel-like cyme; bracts scarious; pedicels in fruit widely spreading; petals 0 |
| S. umbellata |
| | 8' Flowers solitary in axils or few–many in terminal cyme; bracts leafy; pedicels in fruit often recurved to reflexed; petals present or 0 |
| |
| | 9. Flowers solitary in axils; leaf blade ± ovate |
| |
| | 10. Sepals generally 5, acute or acuminate, ribs in fruit 3; leaf margin ± wavy, glabrous; seeds 0.8–1 mm |
| S. crispa |
| | 10' Sepals generally 4, ± obtuse, ribs obscure; leaf margin ± flat, generally ciliate near base; seeds 0.6–0.7 mm |
| S. obtusa |
| | 9' Flowers generally few–many in terminal or axillary cymes; leaf blade lanceolate to ovate |
| |
| | 11. Leaf blade lanceolate to widely so, primary blades mostly > 2 cm, margin papillate (at 20× magnification), dull; stem generally finely papillate; sepals 3–3.5 mm, < 4.5 mm in fruit, ribs in fruit generally 3 |
| S. borealis subsp. sitchana |
| | 11' Leaf blade elliptic to ovate, primary blades mostly < 2 cm, margin ± smooth, shiny; stem not finely papillate; sepals 1.5–3 mm, < 2.5 mm in fruit, veins generally obscure |
| S. calycantha
|