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A deciduous shrub, with slender creeping stems, prickly, and covered with a whitish bloom when young. Leaves usually composed of three leaflets which are green and slightly hairy on both sides. Flowers white, in small clusters. Fruit composed of a few large carpels, covered with a blue-white bloom when ripe.
This is one of the British brambles easily distinguished from all the forms of common blackberry by the few but large ‘pips’ composing the fruit, and by their being covered, like the young stems, with a white or bluish bloom. It is common in Britain and over Europe, extending into N. Asia. Of no value for gardens.
R. caesius hybridises with the true blackberries, and in that way numerous minor species have arisen of intermediate character. Twenty of these are recognised by W. Watson in his treatment of the British Rubi, of which the most interesting is R. balfourianus Bab., which probably arose originally from a cross between R. caesius and R. gratus. Not only are the pink or white flowers sometimes as much as 2 in. wide, but they are borne throughout the summer and early autumn, and the fruits, though often abortive, are sometimes large, with a mulberry flavour (Watson, Handbook of the British Rubi (1958), p. 54 and fig. 3). Apart from these microspecies of hybrid origin, normal hybrids between the dewberry and the blackberries occur; usually these are infertile, but a single individual can cover a wide area by tip-layering.