Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Berberis sieboldii' from the website Trees and Shrubs Online (treesandshrubsonline.
A deciduous shrub of rounded form, usually below 3 ft in height, with reddish branches armed with slender spines up to 1⁄2 in. long. Leaves thin, varying from narrowly obovate to oval, 1 to 21⁄2 in. long, tapered at the base to a short stalk, the margins crowded with fine bristles. Flowers pale yellow, 1⁄3 in. across, in short umbel-like racemes. Fruit globose, about 1⁄5 in. across, yellowish red, shining as if glazed.
Native of Japan. It is an attractive small shrub of suckering habit, which colours well in the autumn if planted in a dry and sunny position. It is not common in cultivation, B. regeliana (q.v. under B. vulgaris) usually doing duty for it.