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An evergreen, glabrous shrub up to 6 ft high and wide; shoots strongly ribbed or angled, pale brown; spines three-parted, 1⁄2 to 1 in. long, stiff. Leaves oval to narrowly oval, tapered to both ends, 1 to 2 in. long, 1⁄4 to 3⁄4 in. wide, edged with small, sharp teeth, conspicuously veined. Flowers rich yellow, 1⁄3 in. across, crowded in axillary, compact clusters of eight to twelve, opening in late March and April; stalks about 1⁄4 in. long; petals five or six, notched at the rounded apex, giving the flowers a globose shape through being more or less concave; sepals very narrow, red at the back. Fruits oval, about 1⁄4 in. long, dark blue. Bot. Mag., t. 9622.
Native of Formosa; introduced by Wilson about 1918 and again by Yashiroda some twenty years later. It belongs to the Wallichianae group of barberries and being quite hardy, free and handsome in bloom, is well worth cultivating.
Dr Ahrendt in his monograph draws a distinction between typical B. kawakamii, which has, according to him, an impressed, reticulate venation and epruinose fruits, and var. formosana (Ahrendt) Ahrendt (B. formosana Ahrendt), to which he refers the cultivated plants, with the leaves not reticulate and the berries conspicuously pruinose. But the distinction is not recognised by Li in Woody Flora of Taiwan. In cultivation the species may have dark blue fruits, as described in the main work, or fruits that are bluish white from the dense bloom covering them. A good spotting character as the flowers open is the very narrow sepals, giving to the buds ‘an unusually prickly appearance’ (Ahrendt).