4. Gleditsia triacanthos Linnaeus, Sp. Pl. 2: 1056. 1753.
美国皂荚 mei guo zao jia
Trees or small trees, to 45 m tall. Bark grayish black, 1-2 cm thick, with deep cracks and narrow, long ridges. Branchlets deep brown, rough, slightly sulcate, with small, orbicular lenticels. Spines deep brown, slightly flat, robust, often branched, 2.5-10 cm, rarely branchlets unarmed. Leaves pinnate or bipinnate (pinnae 4-14 pairs), 11-22 cm; petiolules ca. 1 mm, pubescent; leaflets 11-18 pairs, abaxially yellowish green, adaxially dark green, shiny, elliptic-lanceolate, 1.5-3.5 cm × 4-8 mm, papery, abaxially puberulent on midvein, adaxially glabrous, base cuneate or slightly rounded and oblique, margin sparsely undulate-dentate, apex acute, sometimes slightly obtuse. Flowers yellowish green. Pedicels 1-2 mm. Male flowers: 6-7 mm in diam., solitary or several clustered in racemes; inflorescences terminal or often several fascicled in axils of leaves, 5-13 cm, puberulent; receptacle ca. 2 mm; sepals 2 or 3, lanceolate, 2-2.5 mm; petals 3 or 4, ovate or ovate-lanceolate, ca. 2.5 mm, as sepals puberulent on both surfaces; stamens 6-9. Female flowers: in slender, few-flowered racemes, racemes solitary and ca. as long as male inflorescence; ovary hoary. Legume compressed, strap-shaped, 30-50 cm, falcately curved or irregularly twisted, valves thin and rough, dark brown, pilose. Seeds numerous, compressed, ovoid or elliptic, ca. 8 mm, divided by thick pulp. Fl. Apr-Jun, fr. Oct-Dec. 2n = 28.
Along streams on moist sites, fertile soils. Cultivated in Hong Kong and Shanghai [native to the Americas].
This species is cultivated in temperate regions as an ornamental and used as a wayside tree and hedge. The wood is durable and used for buildings and for props.