Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Rhamnus costata' from the website Trees and Shrubs Online (treesandshrubsonline.
A deciduous shrub, ultimately 15 ft high, of spreading habit; young shoots glabrous, stout. Leaves opposite, ovate-oblong, pointed, tapering below to a narrowly heart-shaped or cuneate base; unevenly and shallowly toothed, 3 to 5 in. long, 11⁄4 to 21⁄2 in. wide, pale green on both sides, strongly ribbed, ribs about twenty, upper surface wrinkled, and furnished with a few hairs, when quite young; undersurface downy, especially on the ribs; stalk about 1⁄8 in. long, downy on the upper side. Flowers green, few or solitary on slender, glabrous stalks, 3⁄4 to 11⁄4 in. long, produced at the base of the young shoots. Fruits top-shaped, black, 1⁄3 in. across, two-seeded.
Native of Japan; introduced in 1900. One of the handsomest of buckthorns in foliage, and belonging to the many-veined group, which includes R. fallax and R. imeritina. From R. fallax it is distinguished by its downy leaves, and from both by the long flower-stalk and strongly wrinkled upper surface of the leaf. It has also a very short leaf-stalk.