Several taxa are cultivated in addition to those recorded here as rarely escaped in Michigan; specimens suspected of being alien and not clearly matching the species below should be checked in works on cultivated plants.
1. Flowers on long pedicels in umbel-like racemes or simple umbels; flowering in early to mid-spring; petals white; cultivated and rarely escaped.
2. Flowers 3–8 in a sessile umbel; leaf blades widest at or below the middle, teeth inconspicuous.
2. Flowers ca. 8–30 in peduncled, umbel-like racemes; leaf blades widest at or above the middle, often with a few coarse teeth on the upper half and sometimes ±3-lobed.
3. Follicles glabrous, lowest inflorescence branches always with single flowers; leaves with ca. 6–15 teeth above the middle, sometimes ± 3-lobed.
3. Follicles finely pubescent, lowest branches of inflorescences often again umbellate; leaves at most with a few teeth at the apex.
1. Inflorescence a branched panicle or corymb; flowering in midsummer; petals pink or (only in common native species) white.
4. Flowers in a broad corymb wider than long; floral tube pubescent; leaves glabrous beneath; flowers bright pink.
4. Flowers in an elongate cylindrical to conical panicle; floral tube, leaves, and flowers not combined as above.
5. Leaves beneath and inflorescence densely tomentose.
5. Leaves and often inflorescence nearly or quite glabrous.
6. Petals white (stamens may give a pinkish cast to the flowers); common native species of usually wet ground.
6. Petals bright pink or rose; rare escape from cultivation.