| | 1. Leaves lanceolate to ovate, clasping, margin clearly glandular or gland-toothed |
| |
| | 2. Petals yellow; leaves whorled or opposite at base, alternate above base, early deciduous, lanceolate, keeled, margin with 1 or 2 rows of gland-tipped teeth, pedicels generally 5–15 mm |
| H. adenophyllum |
| | 2' Petals white to pink; leaves whorled at base, opposite above base, persistent in flower, ovate, flat, margin with 1 row of small glands, pedicels 1–5 mm |
| H. drymarioides |
| | 1' Leaves thread-like to linear, not clasping, margins minutely glandular |
| |
| | 3. Styles 2 (ovary chambers 4) |
| |
| H. bicarpellatum |
| | 4' Petals white or light pink |
| H. didymocarpum |
| | 3' Styles 3 (ovary chambers 6) |
| |
| | 5. Petals, anthers, and styles yellow |
| |
| | 6. Petals 0.5–1.5 mm, styles generally < 1 mm, included, petals and filaments generally = sepals |
| H. clevelandii |
| | 6' Petals 2–12 mm, styles 2–10 mm, exserted, petals and filaments generally >> sepals |
| |
| | 7. Inflorescence short, dense, pedicels 0.2–2 mm, petals 4–10 mm |
| H. breweri |
| | 7' Inflorescence long, open, pedicels 2–10 mm, petals 2–5.5 mm |
| |
| | 8. Herbage hairy only at nodes, petals 2–3.5 mm, tip slightly notched |
| H. serpentinum |
| | 8' Herbage hairy, petals 3.5–5.5 mm, tip deeply notched |
| H. tehamense |
| | 5' Petals, anthers, and styles white to deep purple |
| |
| | 9. Inflorescence short, dense, pedicels 1–8 mm |
| |
| | 10. Sepals glabrous outside, petals white to pink-veined |
| H. californicum |
| | 10' Sepals hairy outside, petals light to dark pink |
| H. congestum |
| | 9' Inflorescence long, open, pedicels 1–25 mm |
| |
| | 11. Petals 0.5–3.5 mm, styles generally < 1 mm, included, petals and filaments generally = sepals |
| H. micranthum |
| | 11' Petals 3–7 mm, styles 3–6 mm, generally exserted, petals and filaments generally >> sepals |
| |
| | 12. Pedicels straight or erect, 1–5 mm, petals 3–6 mm |
| H. disjunctum |
| | 12' Pedicels generally pendent or ± reflexed, 6–25 mm, petals 4–7 mm |
| H. spergulinum
|