Gleditsia triacanthos L.

  • Authority

    Isley, Duane. 1975. Leguminosae of the United States: II. Subfamily Caesalpinioideae. Mem. New York Bot. Gard. 25 (2): 1-228.

  • Family

    Caesalpiniaceae

  • Scientific Name

    Gleditsia triacanthos L.

  • Description

    Species Description - Armed or usually in cultivation unarmed medium to large trees. Leaves 2-pinnate and alternate on new terminal growth, and 1-pinnate and fascicled from spurs on older wood. Leafstalk 1-2 dm, conspicuously puberulous. Bipinnate leaves with 2-6(-8) pairs pinnae; leaflets (2-)5-8(-10) pairs, elliptic-oblong, mostly 1.3-2(-2.5) cm, pinnately nerved, initially puberulous, glabrate at maturity. Once-pinnate leaves 3-6 from spurs with 10-14 pairs, 1.5-3(-3.5) cm leaflets. Level of armament variable, the thorns to 2 dm, shiny brown, subterete but flattened at base, simple to much branched, often forming a thorny mantle on trunks and major branches. Staminate inflorescences preponderant, 1-several from spurs, simple or apically branched, (1-)3-5(-7) cm with numerous, crowded, subsessile to briefly pedicelled flowers densely golden-puberulent before anthesis; fertile inflorescences solitary, villosulous, 3-5(-8) cm, with spaced and pediceled (4-8 cm) flowers. Perianth-hypanthium ca 3 mm (staminate) or 4-5 mm (pistillate); stamens 5-7. Legumes 1-3 per peduncle, essentially indehiscent and persistent past end of growing season, stipitate, oblong, laterally compressed but plump, straight or curved through 90°, 2-4 dm long, 2.5-3(-4) cm wide; valves initially pubescent and pulpy, becoming shiny brown, dry, often twisted or contorted at maturity. Seeds many, ca 9 mm long, 5 mm wide.

  • Discussion

    G. horrida Hort. p.p. G. sinensis Hort. p.p. G. amorphoides Hort. p.p. CN 2n = 28 (Atchison, 1947; 33 collections from throughout much of natural range); n = 14 (Gordon, 1970). And others. Gleditsia triacanthos was perhaps originally largely restricted to bottom lands, and has invaded the uplands as a consequence of man’s activities. Presently one finds it from river bottoms to upland pastures, in thickets and along fence rows. The honey locust is now among the most common urban shade and foliage trees in the central and eastern states, in part serving as a replacement for the American elm, ravaged by the Dutch elm disease. It is frequent along highways in plains and mountain states both as an ornamental and for windbreak, and is increasingly planted in the Pacific states. All the numerous horticultural cultivars (Wagenkencht, 1961) represent unarmed forms. They do not deserve varietal recognition in the usual botanical sense inasmuch as armature does not breed true (Deam, 1940); the level seems to be quantitative, and thornless forms are sporadic throughout the range of species (Deam, 1940; Gordon, 1966). For convenience G. triacanthos f. inermis Schneider can serve to distinguish collectively all thornless forms of the species, wild or cultivated.

  • Distribution

    C and s United States e to Appalachians; s New York, e Nebraska, e Texas, n Florida. Cult, within and beyond this range. Moist woodlands of river and creek bottoms and adjacent slopes, also disturbed open, drier upland woodlands, pastures, roadsides etc., common. Much planted in towns, in some states (e.g. Nebraska) conspicuous along highways. April-May. Honey locust and various horticultural names as Sunburst locust, Moraine locust. Introduced in temperate Old World.

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