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A deciduous shrub of graceful spreading habit 6 to 8 ft high; young shoots slender, downy, pinkish at first, becoming black-brown the second year. Leaves ovate, up to 2 in. long by 1 in. wide on the virgin shoots, smaller and narrower on the flowering ones, not toothed, pointed, tapered at the base, glabrous above, hairy on the midrib and veins and paler beneath, three-veined; stalk 1⁄8 in. or less long, downy. Flowers solitary or in threes, terminating leafy twigs 1 to 2 in. long, white, 11⁄4 in. wide. Calyx-tube hemispherical, the four lobes ovate, about 1⁄4 in. long, covered with silvery-grey down; petals obovate; anthers greenish; styles united, stigmas free; ovary quite glabrous.
Native of New Mexico; discovered in 1892, introduced in 1922. This charming philadelphus is related to P. microphyllus and the flowers have a similar fruity fragrance, but that species has a nearly glabrous calyx whilst in this it is silvery grey with down; P. argyrocalyx has also larger flowers and a more vigorous growth. It is very pretty in bloom, the flowers showing in two rows on the upper side of the previous year’s (usually arching or drooping) shoots. Flowering in late June and July, being perfectly hardy and of a convenient size, it deserves to be more widely planted.