Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Rubus trianthus' from the website Trees and Shrubs Online (treesandshrubsonline.
A deciduous shrub of wide-spreading habit, the biennial stems erect, much branched, spiny, blue-white, 4 to 6 ft high. Leaves simple, 3 to 6 in. long, 11⁄2 to 41⁄2 in. wide, ovate to triangular, distinctly three-lobed on the barren stems, less markedly lobed on the flowering shoots, middle lobe long, taper-pointed, irregularly toothed, quite glabrous on both sides, whitish beneath, dark green above; there are hooked spines on the midrib and veins beneath; stalk 1⁄2 to 11⁄2 in. long, similarly armed. Flowers pinkish white, insignificant, produced a few together on cymes that are terminal on short lateral twigs. Fruits dark red.
Native of Central China up to 4,000 ft; introduced for Messrs Veitch by Wilson in 1900. It is distinct from most Rubi in the absence of down or hairs, but has not much garden value.