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A deciduous shrub 4 to 6 ft high, with rigid, spreading branches; young shoots glabrous, distinctly angled. Leaves oblanceolate to oblong, abruptly pointed, tapered at the base, with a few teeth near the apex or none at all; 1 to 21⁄2 in. long, 1⁄2 to 1 in. wide, vivid green above, rather glaucous beneath, quite glabrous; stalk 1⁄4 in. or less long. Flowers white, 1⁄3 in. wide, produced during June on rounded corymbs 1 to 2 in. wide, growing upwards, and terminating short leafy twigs that are clustered on the preceding year’s shoots, the whole forming a handsome arching spray sometimes over 1 ft long. Petals roundish, notched; flower-stalks and seed-vessels downy.
Native of Korea; discovered in 1902; introduced to cultivation in 1917 from the Diamond Mountains by Wilson, who considered it one of the best of all spiraeas. It is distinct in its glabrous, nearly entire leaves, very pale beneath. It is considered to be nearest to S. nipponica and has similar leafy bracts on the inflorescence, but S. nipponica has much shorter, more oval leaves and a more compact, less spreading habit. S. trichocarpa thrives in the garden of the late E. H. M. Cox at Glendoick in Perthshire, where it has grown since Wilson introduced it, and flowers well every year even where densely shaded in summer (E. H. M. and P. A. Cox, Modern Shrubs (1958), p. 169; see also New Fl. and Sylva, Vol. I (1928), pp. 12-13 and fig. iii; Gard. Chron. Vol. 74 (1923), p. 87 and fig. 32).
This species received an Award of Merit in 1942.