1. Berberis canadensis Mill. (American barberry)

Pl. 302 b, c; Map 1269

Shrubs 40–200 cm tall. Second-year twigs with the bark purple or brown; spines simple or pinnately 3(–7)-branched. Petioles 2–8(–13) mm long. Leaf blades 1.8–7.5 cm long, 0.8–3.3 cm wide, oblanceolate or sometimes narrowly elliptical, long-attenuate at the base, rounded or bluntly pointed at the tip, each margin with 3–12 bristle-tipped teeth. Inflorescences lax racemes 2.0–5.5 cm long, with 3–12 flowers. Fruits 10 mm long, red, oblong-ellipsoidal. 2n=28. May.

Uncommon, restricted to the south-central portion of the Ozark Division (Pennsylvania to Missouri south to Georgia and Tennessee). Ledges of dolomite bluffs and blufftop glades, occasionally on sandstone near the contact zone with dolomite strata.

Berberis canadensis is uncommon enough to be considered imperiled in Missouri and elsewhere in its range, but it is susceptible to infection by Puccinia graminis and is legally subject to eradication. Because it is uncommon and grows in areas remote from farms, it has no impact on grain farming in the state, so this native species should be exempted from eradication. Despite its scientific name, B. canadensis is not found in Canada.