A deciduous unarmed shrub 6 to 8 ft high, of lax, rather gaunt habit, spreading by means of underground suckers, the branches covered with gland-tipped bristles 1⁄6 in. long. Leaves pinnate, 6 to 10 in. long; leaflets seven to thirteen, each 11⁄2 to 21⁄2 in. long, and from 3⁄4 to 11⁄2 in. wide, oval or ovate with a short bristle-like tip, very dark green; stalk hairy. Racemes 2 or 3 in. long, nearly as much wide, carrying five to ten flowers. The flowers are the largest and most showy among robinias, each about 11⁄4 in. long, with the rounded standard petal as much across, of a lovely deep rose; calyx 1⁄2 to 2⁄3 in. long, with long, slender, awl-shaped teeth, and bristly like the flower-stalk. Pods 11⁄2 to 21⁄2 in. long, 1⁄3 in. wide, thickly covered with gland-tipped bristles. Blossoms in May and June. Bot. Mag., t. 311.
Native of the south-eastern United States; introduced in 1743. In the wild it spreads and renews itself by means of sucker-growths extending several feet in a single season, but in cultivation it is usually grafted as a standard on R. pseudacacia so as to form a low, bushy-headed tree. Undoubtedly one of the loveliest of all trees of that character, it is, unfortunately, very liable to lose its branches during storms, owing to the brittle nature of its wood. For this reason a secluded spot is desirable for it. A remarkable fact in connection with this tree is the rarity with which it produces seed. It has probably never borne pods in this country, and even in the wild they are very seldom seen. The pods in the Kew Herbarium are three contributed by T. Meehan of Philadelphia, to whom they had been sent in response to inquiries made in a public journal. He himself had made diligent search for seed-pods on the mountains of Tennessee, where the shrub grows in great abundance, but never found any. The defect seems to be in the male part of the flower, and due to the absence of pollen.
var. fertilis (Ashe) Clausen R. fertilis Ashe – Leaflets relatively narrower, elliptic or oblong-ovate, often acute, downy beneath. A more important difference is that this variety sets fertile seed. A parent of ‘Monument’, see below.
cv. ‘Macrophylla’. – This is distinguished chiefly by the branches and leaf-stalks being nearly or quite free of bristles. The stalks of the racemes and flowers are hairy, but by no means as markedly as in the type. The flowers are even larger and more brightly coloured, the leaflets rounder (R. macrophylla Hort.; R. hispida var. macrophylla DC.; R. h. f. inermis Kirchn.).
cv. ‘Monument’. – A compact shrub to 10 or 12 ft high, with rosy lilac flowers. Raised in the USA from var. fertilis, which it resembles in foliage. Also known as R. fertilis ‘Monument’.