| | 1. Annual; petioles ± long, well developed |
| |
| | 2. Phyllaries generally > 4 mm wide, abruptly acuminate; leaf base cordate |
| H. annuus |
| | 2' Phyllaries generally < 4 mm wide, acute or gradually acuminate; leaf base generally truncate to wedge-shaped |
| |
| | 3. Central chaff scales tipped with stiff white hairs |
| |
| | 4. Herbage and phyllaries densely gray-canescent |
| H. niveus subsp. canescens |
| | 4' Herbage and phyllaries strigose, green |
| H. petiolaris subsp. petiolaris |
| | 3' Central chaff scales glabrous or very finely appressed-hairy |
| |
| | 5. Chaff scales awn-tipped, >> disk flowers, glabrous; leaves green |
| H. bolanderi |
| | 5' Chaff scales acute, = or slightly > disk flowers, rough-hairy; leaves densely white-hairy |
| 2 H. niveus subsp. tephrodes |
| | 1' Perennial; leaves sessile (or petiole < 3 cm) |
| |
| | 6. Disk corolla lobes red to purple |
| |
| | 7. Leaves blue-green, ± glabrous, margins often crinkled; roots horizontal, rhizome-like; ligules generally < or = 1 cm; phyllaries < disk |
| H. ciliaris |
| | 7' Leaves green or densely white-hairy, margins generally flat; plant taprooted; ligules generally >> 1 cm; phyllaries = or > disk |
| |
| | 8. Leaves green, short-rough-hairy; phyllaries not > disk |
| 2 H. gracilentus |
| | 8' Leaves densely white-hairy; phyllaries = or slightly > disk |
| 2 H. niveus subsp. tephrodes |
| | 6' Disk corolla lobes yellow |
| |
| | 9. Phyllaries not > disk, obtuse to acute |
| 2 H. gracilentus |
| | 9' Phyllaries > disk, acuminate |
| |
| | 10. Phyllaries generally 12–18; most leaves opposite, generally < 12 cm; plants tap-rooted |
| H. cusickii |
| | 10' Phyllaries generally > 25; most leaves alternate, often > 15 cm: plants rhizomed |
| |
| | 11. Leaf blades folded along midvein; inflorescence generally raceme-like |
| H. maximilianii |
| | 11' Leaf blades ± flat; inflorescence flat-topped or rounded |
| |
| | 12. Phyllaries generally 3+ mm wide, folded back at maturity; stem generally glabrous |
| H. californicus |
| | 12' Phyllaries generally < 3 mm wide, ± erect at maturity; stem generally ± hairy |
| H. nuttallii |
| | 13. Phyllaries sparsely hairy; leaf blade short-rough-hairy below |
| subsp. nuttallii |
| | 13' Phyllaries densely hairy; leaf blade finely tomentose below |
| subsp. parishii
|