刺槐 ci huai

Robinia pseudoacacia var. inermis Candolle; R. pseudo­acacia var. pyramidalis (Pepin) C. K. Schneider; R. pseudo­acacia var. umbraculifera Candolle; R. pyramidalis Pepin.

Trees, 10-25 m tall, deciduous. Bark gray-brown to dark brown, longitudinally fissured, rarely smooth. Branchlets gray-brown, sparsely hairy, glabrescent; stipulate spines up to 2 cm; winter buds small, with hairs. Leaves 10-25(-40) cm; rachis adaxially grooved; petiolule 1-3 mm; stipel acicular; leaflets 2-12 pairs, usually opposite or subopposite; leaflet blades oblong, elliptic, or ovate, 2-5 × 1.5-2.2 cm, abaxially grayish green and with appressed pubescence when young but glabrescent, adax­ially green, base rounded to broadly cuneate, margin entire, apex rounded, retuse, and apiculate. Racemes axillary, 10-20 cm, pendulous, many flowered, fragrant; bracts caducous. Pedi­cel 7-8 mm. Calyx obliquely campanulate, 7-9 mm; teeth 5, triangular to ovate-triangular, densely appressed pubescent. Co­rolla white, stipitate; standard suborbicular, ca. 1.6 × 1.9 cm, re­flexed, inside with yellow spots, base rounded, apex with a sinus; wings obliquely obovate, subequal to standard, ca. 16 mm, one lateral auriculate rounded; keel falcate, triangular, equal to wings or slightly short, connate at leading edge, obtuse. Stamens diadelphous, one opposite to standard free. Ovary line­ar, ca. 1.2 cm, glabrous; stalk 2-3 mm; style subulate, ca. 8 mm, apically curved, apex piliferous; stigma terminal. Legume brown or with reddish brown stripes, linear-oblong, 5-12 × 1-1.3(-1.7) cm, compressed, apex volute and mucronate, carpo­podium short, narrow wings along ventral suture; calyx persis­tent, 2-15-seeded. Seeds brown to dark brown, slightly glossy, sometimes with stripes, subreniform, 5-6 × ca. 3 mm; hilum rounded, oblique to one end. Fl. Apr-Jun, fr. Aug-Sep. 2n = 20, 22.

Cultivated in all of China except Hainan and Xizang [native to E North America; cultivated and sometimes naturalized in many parts of the world].