Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Berberis canadensis' from the website Trees and Shrubs Online (treesandshrubsonline.
A deciduous shrub 3 to 6 ft high, with the branchlets not downy, but thickly covered with small, warty lenticels, and armed with three-parted spines. Leaves narrowly obovate, from 1 to 21⁄2 in. long, tapering very gradually at the base, the apex rounded or acute, but always terminating in a short spine, the margin toothed, sometimes remotely so, sometimes almost entire, glabrous. Racemes 1 to 11⁄2 in. long, bearing from six to fifteen yellow flowers. Fruit oval or nearly globose, red.
The specific name of this barberry is a misnomer, for it does not appear to be a native of any part of Canada, its real home being on the slopes of the Allegheny Mountains in Virginia, N. Carolina, etc., where it is most often found on the banks of mountain streams. In general appearance it is not unlike the Old World B. vulgaris, but it is not quite so attractive a shrub; it differs in its paler and more glaucous leaves, its smaller flowers, its shorter, almost corymbose racemes, and in its shorter, rounder fruit. It has been cultivated in this country since the middle of the eighteenth century, but is now rarely seen.