| | 1. Fruit not long-tapered at base, glabrous; leaf 2-pinnate (subg. Glycosma) |
| O. occidentalis |
| | 1' Fruit long-tapered at base into tail, bristly; leaf 2–3-ternate (subg. Osmorhiza) |
| |
| | 2. Involucel conspicuous; corolla greenish yellow |
| O. brachypoda |
| | 2' Involucel 0 or vestigial; corolla white or purple, rarely greenish white |
| |
| | 3. Fruit club-like, beakless; rays, pedicels spreading |
| O. depauperata |
| | 3' Fruit linear-fusiform or -oblong, beaked; rays, pedicels spreading-ascending |
| |
| | 4. Projection atop ovary conic; disk 0; fruit 12–25 mm; corolla white |
| O. berteroi |
| | 4' Projection atop ovary depressed-conic; disk conspicuous; fruit 8–15 mm; corolla purple, rarely greenish white |
| O. purpurea
|