| | 1. Perennial or subshrub from woody root-crown |
| H. whitneyi |
| | 2. Heads discoid; disk achenes < 10 mm |
| var. discoidea |
| | 2' Heads radiate; disk achenes generally 5–8 mm |
| var. whitneyi |
| | 1' Shrubs; stems arising from woody trunk |
| |
| |
| | 4. Ray flowers >> disk flowers; leaf margin entire |
| H. orcuttii |
| | 4' Ray flowers < disk flowers; leaf margin generally subentire to toothed |
| |
| | 5. Leaves soft-hairy to scabrous; plant 2–8 dm |
| H. brickellioides |
| | 5' Leaves densely tomentose, at least below; plant 6–25 dm |
| |
| | 6. Leaves thin, becoming glabrous above; phyllary tips loosely woolly-tufted; disk corollas 5–8 mm |
| H. cana |
| | 6' Leaves thick, densely tomentose above; phyllaries generally densely woolly throughout; disk corollas 8–10 mm |
| H. detonsa |
| |
| | 7. Flowers 4–8; leaves 15–25 mm, 7–12 mm wide |
| H. stenolepis |
| | 7' Flowers 9–30; leaves 15–50 mm, 10–20 mm wide |
| H. squarrosa |
| | 8. Herbage generally sparsely hairy, generally not resinous; involucres 8–12 mm; flowers 9–16, corollas 9–10 mm; pappus white to reddish brown |
| var. grindelioides |
| | 8' Herbage glabrous to sparsely hairy, generally resinous; involucres 11–15 mm; flowers 18–30, corollas 10–11 mm; pappus tan |
| |
| | 9. Stems glabrous to scabrous; phyllaries smooth, resinous, ± obtuse, abruptly pointed, ± erect |
| var. obtusa |
| | 9' Stems sparsely hairy above or becoming glabrous; phyllaries glandular, obtuse to acute, recurved |
| var. squarrosa
|