Trees [shrubs], armed or unarmed, trunk and branches with simple or compound thorns or thornless. Stems erect. Leaves alternate, usually even-bipinnate on new growth and main branches or even-pinnate from spur shoots, rarely odd-pinnate or -bipinnate, sometimes abnormally large, unifoliolate; stipules present; petiolate; pinnae 2–6(–8)[–10] pairs, increasing in length distally; leaflets (1–)4–32, blade margins usually crenulate, rarely entire or irregularly crenulate, surfaces glabrous or pubescent. Inflorescences 5–100-flowered, axillary, racemes in spicate clusters; bracts present, caducous. Flowers caesalpinioid; calyx bell-shaped, lobes 3–5; corolla petals 3–5, not obvious, greenish [white]; stamens 3–7(–10), distinct, inserted with petals on margin of disc; anthers dorsifixed. Fruits legumes, stipitate, flat or compressed and plump, straight or falcate, sometimes twisted, short-ovate or oblong, ± indehiscent, papery or woody, glabrous or pilose. Seeds 1–25(–30), transverse, compressed to subterete, orbicular or ovoid-elliptic. x = 14.

Distribution

North America, s South America, e, se, w Asia, w Africa, warm temperate, subtropical, or tropical areas within northern temperate zone, introduced in South America, Europe, Australia.

Discussion

Species ca. 16 (2 in the flora).

Gleditsia is of timber importance; the pulp of the pods has been used to make soap. Gleditsia triacanthos (honey-locust) is frequently cultivated in gardens and arboreta. In urban plantings thornless forms (= forma inermis Zabel) are primarily used. D. C. Michener (1986) argued against the taxonomic recognition of such forms in G. triacanthos, citing phenotypic instability that results in a continuum of thorn production, including reversion in mature, previously thornless individuals.

Gleditsia has also received favor as a fodder tree due to its production of large, sweet legumes that are valued by cattle and other livestock. This modern day preference by livestock is a contemporary phenomenon, facilitated by human agricultural practice. D. H. Janzen and P. S. Martin (1982) described the anachronistic nature of large-fruited trees, such as Gleditsia triacanthos and Gymnocladus dioicus, which quite likely had much larger and more dense distributions when their coevolved megafaunal dispersers existed.

Fruit extract of Gleditsia sinensis Lamarck from Asia has demonstrated promise in the treatment of multiple forms of cancer (L. M. C. Chow et al. 2003).

Phylogenetic studies show that Gleditsia as monophyletic, in the Umtiza clade, and sister to Gymnocladus. Both genera show fragmented, relictual distributions (A. Schnabel et al. 2003; G. P. Lewis 2005).

Gleditsia × texana Sargent is a hybrid between G. aquatica and G. triacanthos that shows a range of morphological intergradation between the two parents even within a single site (C. S. Sargent 1922; B. A. Smith and D. L. Marsh 1993). It is distinguished by: trees to 36 m,75 cm diam.; leaves pinnate or bipinnate, 15 cm, pinnae 3–7, leaflets 8–15 pairs, blades 1.5–2.5 cm, surfaces pale green abaxially, dark green and shiny adaxially; racemes 8–10 cm; staminate flowers with yellow corollas, stamens exserted, anthers green; legumes straight, 10–15 × 2 cm, usually pulpless, with oblique and rounded base and blunt apex, surfaces puberulent; seeds many, compressed, and elliptic. The hybrid is known from Arkansas, Florida, Indiana, Louisiana, Mississippi, South Carolina, and Texas.

Selected References

None.

Lower Taxa

Gleditsia aquatica, Gleditsia triacanthos

Key

1	Legumes ovate, 3–5(–8) cm, straight; seeds 1[–3].	Gleditsia aquatica
1	Legumes oblong, 20–40 cm, straight or slightly twisted; seeds 4–25(–30).	Gleditsia triacanthos