| | 1. Inflorescence a cyme, generally appearing with or after leaves; petal-like bracts 0 |
| |
| | 2. Leaf generally 3–5 cm, veins 3–4 pairs |
| C. glabrata |
| | 2' Leaf generally 5–10 cm, veins 4–7 pairs |
| C. sericea |
| | 3. Leaf generally densely rough-hairy beneath; petals 3–4.5 mm; stone generally with 3 wide ridges on each face |
| subsp. occidentalis |
| | 3' Leaf generally ± glabrous or strigose beneath; petals 2–3 mm; stone generally smooth |
| subsp. sericea |
| | 1' Inflorescence a head or umbel, generally appearing before leaves; ± petal-like bracts present |
| |
| | 4. Inflorescence subtended by 4 ephemeral, ± brownish, not very petal-like bracts |
| C. sessilis |
| | 4' Inflorescence subtended by 4–7 persistent, whitish, showy, petal-like bracts |
| |
| | 5. Herb or subshrub from rhizomes; bracts 4, ± 1.5 cm; fruit generally ± 8 mm, spheric |
| C. canadensis |
| | 5' Shrub or tree; bracts 4–7, ± 5 cm; fruit generally 10–15 mm, elliptic in outline |
| C. nuttallii
|