Rhamnaceae, the Buckthorn Family
Shrubs, with simple leaves and small flowers in axillary or terminal clusters in early summer; sepals, petals, and stamens each 4 to 5, or petals none.
| 1a. Leaves with a single mid-vein; flowers in axillary clusters, greenish (Buckthorn) — 2. | |
| 1b. Leaves with 3-5 principal veins; flowers in dense terminal clusters, white (Red-root) — 3. | |
| 2a. Lateral veins 3-4 pairs (stout shrub, frequently thorny, escaped from cultivation) | Buckthorn, Rhamnus cathartica. |
| 2b. Lateral veins 6-9 pairs (1 m. high or less; in swamps and bogs) | Buckthorn, Rhamnus alnifolia. |
| 3a. Leaves ovate, rounded or cordate at the base, 2-5 cm. wide or more (4-8 dm. high) | Red-root, Ceanothus americanus. |
| 3b. Leaves elliptical-lanceolate, 2 cm. wide or less (3-8 dm. high) | Red-root, Ceanothus ovatus. |