A tree, sometimes 20°—25° high, with a trunk 6′—8′ in diameter, and branchlets at first pale and coated with rusty brown glandular hairs increasing in length during the summer, and slightly puberulous, bright reddish brown, often covered with a glaucous bloom, and marked by a few small scattered pale lenticels during their first winter. Bark of the trunk thin, slightly furrowed, light brown, the surface separating into small plate-like scales. Wood heavy, exceedingly hard, strong, close-grained, yellow streaked with brown, with light yellow sapwood of 4 or 5 layers of annual growth.
Distribution. Banks of mountain streams; valley of the Purgatory River, Colorado, through northern New Mexico and Arizona to southern Utah; on the Santa Catalina and Santa Rita Mountains, southern Arizona up to altitudes of 7000°; probably of its largest size near Trinidad, Las Animas County, Colorado.
Occasionally cultivated as an ornamental tree in the eastern states, and in western Europe.
× Robinia Holdtii Beiss, a hybrid of Robinia neo-mexicana var. luxurians and R. Pseudoacacia, has appeared in a Colorado nursery and is occasionally cultivated.
3. [Robinia viscosa] Vent. Clammy Locust.
Leaves 7′—12′ long, with a stout nearly terete dark glandular-hispid clammy petiole, and 13—21 leaflets; stipules subulate, chartaceous, often deciduous or developing into short slender spines; leaflets ovate, sometimes acuminate, mucronate, rounded or pointed at apex, and cuneate at base, when they unfold covered below with soft white pubescence, and slightly puberulous above, and at maturity dark green and glabrous on the upper surface, pale and pubescent on the lower surface, especially on the slender yellow midrib and primary veins and on the stout glandular-hispid petiolule, 1½′—2′ long and ⅔′ wide; stipels slender, deciduous. Flowers ⅔′ long, almost inodorous, appearing in June, on slender hairy pedicels from the axils of large lanceolate acuminate dark-red bracts contracted at apex into a long setaceous point exserted beyond the flower-buds and mostly deciduous before the flowers open, in short crowded glandular-hispid racemes; calyx dark red, coated on the outer surface and on the margins of the subulate lobes with long pale hairs; corolla pale rose or flesh color, with a narrow standard marked on the inner face by a pale yellow blotch, and broad wing-petals. Fruit narrow-winged, glandular-hispid, 2′—3½′ long; seeds ⅛′ long, dark reddish brown and mottled.
A tree, 30°—40° high, with a trunk 10′—12′ in diameter, slender spreading branches, and dark reddish brown branchlets covered with conspicuous dark glandular hairs exuding, like those on the petioles and legumes, a clammy, sticky substance, during the first winter bright red-brown, covered with small black lenticels and very sticky, becoming in their second year light brown and dry; or a shrub, often only 5°—6° tall. Bark of the trunk ⅛′ thick, smooth, dark brown tinged with red. Wood heavy, hard, close-grained, brown, with light yellow sapwood of 2 or 3 layers of annual growth.
Distribution. Mountains of North and South Carolina up to altitudes of 3000°, and now naturalized in many parts of the United States east of the Mississippi River and as far north as eastern Massachusetts.
Often planted as an ornament of parks and gardens in all countries with a temperate climate.