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A deciduous shrub 6 to 10 ft high (in the wild over 20 ft). Leaves three-lobed, broadly ovate, 2 to 4 in. long, doubly toothed, downy beneath. Flowers white, produced in a corymb, each flower on a downy stalk about 1⁄2 in. long; calyx very downy. Fruits glabrous or nearly so, composed of three to five inflated pods 1⁄3 in. long, containing usually two obliquely pear-shaped seeds.
Native of western N. America from British Columbia to California, where it is said to have stems often more than 20 ft long interlaced with willow branches, and forming impenetrable thickets on the banks of streams (Greene). It is really a western form of P. opulifolius, from which it differs chiefly in the more downy leaves and in the pear-shaped seeds. Introduced in 1827.