Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Physocarpus monogynus' from the website Trees and Shrubs Online (treesandshrubsonline.
A dwarf deciduous bush about 2 ft high in the wild, with erect, much-branched stems. Leaves 3⁄4 to 11⁄2 in. long, roundish ovate, three-lobed, the lobes irregularly and doubly toothed, sometimes very downy beneath, sometimes only slightly so. Flowers 1⁄4 in. in width, of a clear or slightly rose-tinted white, produced in early June in few-flowered corymbs 3⁄4 to 11⁄4 in. across. Fruits downy, usually composed of two pods cohering for more than half their length, but sometimes only one; each contains one obovoid seed.
Native of the Rocky Mountains of Colorado up to elevations of 9,000 ft. It is a pretty little shrub with small leaves often lobed and toothed, like a ribes. Its dwarf habit, small leaves, and few downy seed-vessels well distinguish it.