A diverse family, sometimes divided into two or more, and of considerable phytogeographic interest, because so many of the herbaceous species of eastern North America have close counterparts in eastern Asia (e.g., Caulophyllum, Jeffersonia, Podophyllum). All species of Berberidaceae should be treated with caution because of their poisonous principles.
1. Plant a woody shrub with the twigs or leaves spiny; leaves simple and unlobed or once-pinnately compound with at least 3 leaflets.
1. Plants herbaceous, spineless; leaves deeply lobed or, if compound, not once-pinnate.
2. Leaves thrice-compound, the leaflets petioluled; flowers yellowish green to purplish, less than 1.5 cm across, several in an inflorescence; “fruit” ca. 1 cm long or less, a blue, fleshy seed (the ovary wall withering away).
2. Leaves of only 2 leaflets or deeply lobed but simple; flowers white, broader, solitary; fruit more than 1 cm long, a many-seeded yellowish berry or a brownish capsule.
3. Leaves all basal, deeply 2-lobed or of 2 sessile leaflets; fruit ca. 1.5–2.5 cm long, a brownish capsule opening (incompletely) transversely near the end, as if by a lid.
3. Leaves cauline, deeply several-lobed; fruit more than 2.5 cm long, a yellowish (to purplish) berry.