Agroforestree Database

Local names:
 English (honey locust,thorny locust,thorn tree,sweet locust,black locust,kirgis honey locust,honey shuck,three-horned acacia,common honeylocust), French (carouge miel,févier épineux), German (Dreidornige Gledischie), Italian (gledischia,spino di Cristo,s

Gleditsia triacanthos attains a normal height of 15-25 (50) m and 0.5-1 (max. 1.8) m diameter. Trees have a short bole and open, narrow or spreading crown, bark reddish-brown to black, scaly, ridged, often covered in clusters of large, branched thorns. It has a strong taproot and a profusely branched root system.

Leaves deciduous, alternate, singly or doubly pinnately compound. Those singly compound form early on dwarf shoots or toward the base of the long shoots; bear 14-30 leaflets (no terminal leaflet) on a central stalk 15-20 cm long; preformed in buds. Those doubly compound bear 4-7 pairs of branches, each resembling a singly compound leaf; neoformed during the growing season. Leaflets 25-40 mm long, widest near the base; tip rounded, often with a small point; sometimes minutely toothed.

Flowers greenish-white, regular, small, about 5 mm across. The male and female flowers on the same tree, often on separate branches. Perfect flowers may also be present. Pollen flowers in many-flowered clusters (racemes) 5-7 cm long. Seed flowers in few-flowered clusters 7-9 cm long. 

Fruit 15-40 cm long pods, flat, curved, twisted, brownish; husk leathery; falling in winter without opening. Seeds beanlike; with a hard, impermeable seed coat; 0.5-1.5 cm long, dark brown, smooth.

The generic name, sometimes spelt Gleditschia, commemorates the German botanist Johan Gottlieb Gleditsch (1714-1786), professor and director of the Berlin Botanic Garden. The specific name ‘tricanthos’ means 3-thorned; from the Greek ‘treis’ (three) and ‘akantha’ (a spine).

Ecology

Within the natural range, a large amount of variation exists in both climate and soil conditions. G. triacanthos occurs naturally in humid and subhumid climate regions; it grows naturally to 760 m but has been planted from sea level to 1500 m in temperate latitudes and will grow above 2500 m in subtropical highlands. It is shade intolerant and will only become established in open spaces. G. triacanthos is resistant to both drought and salinity.

Native range
United States of America

Tree management

Male trees (about 10%) must be included in or adjacent to fodder orchards to ensure pollination of female trees. When established in working pastures, young trees need protection with plastic tree shelters or electric fencing. Appropriately managed, average annual pod production of 40 kg/tree appears feasible. Planting 75 trees/ha (excluding male trees) would yield 3000 kg/ha, sufficient to provide 100 sheep a 1.5-kg ration of pods for 20 days. The tree coppices vigorously when cut. Typical of many caesalpinioid genera, G. triacanthos does not nodulate and lacks the ability for symbiotic fixation of atmospheric nitrogen.

After harvest, pods should be stored at 0 deg. C to prevent fermentation. If bruchid seed weevils (Amblycerus robiniae) are present in the pods, it will prevent them from spreading within the pods. 

Seed storage behaviour is orthodox. A few seeds germinated after 50 years in storage at 4% mc and ambient temperature; viability was maintained for several years in hermetic air-dry storage at 0-8 deg. C. Seed yield averages 5200 seeds/kg (3300-14 300, depending on the seed source) with high purity and soundness.

Within the natural range, a large amount of variation exists in both climate and soil conditions. G. triacanthos occurs naturally in humid and subhumid climate regions; it grows naturally to 760 m but has been planted from sea level to 1500 m in temperate latitudes and will grow above 2500 m in subtropical highlands. It is shade intolerant and will only become established in open spaces. G. triacanthos is resistant to both drought and salinity.

Mature pods can be collected after they drop off, or by hitting branches to jar the pods loose, or by clipping pods from the branches. Successful germination requires seed scarification by immersion in concentrated sulphuric acid (60-120 minutes followed by thorough rinsing), hot water (82 deg. C), or by mechanical means. To prepare pods for mechanical seed extraction, place them in a convection or seed-drying oven for at least 2 hours at 35 deg. C. Germination of sound seed should be in the range of 75-95%. Seeds should be sown 0.5-1.5 cm deep and, if they are properly scarified, complete germination will occur within 21 days. Dormant, nursery-grown seedlings can be stored, bare rooted, at about 0 deg. C for several weeks before planting out.

For successful propagation of G. triacanthos, chip budding with green wood works best. Dormant scionwood results in a low percentage of successful grafts; 1-year-old seedlings (or budded/grafted material) can be out-planted the following spring. Due to large variation in pod production from different parent trees, and the presence of both male and female trees, only grafted seedlings are recommended for planting to secure consistently high production at an early age.

Poison: Triacanthine from the leaves is highly toxic (LD50 about 35 mg/kg) and of questionable oncostatic activity.

Erosion control: Because it can be applied in erosion control, G. triacanthos is being tested in many temperate, Mediterranean and highland tropic regions of the world.

 Seeds have been roasted and used as a coffee substitute.

Fodder: G. triacanthos leaves are an excellent source of fodder, contain 20% crude protein, low lignin and ensile well. Coppice regrowth retains high protein and low lignin levels. It has used as fodder in Australia and elsewhere. However, limited studies indicate very low biomass yield response when planted from seed and harvested with a forage harvester during the 1st year’s growth, or when 1-year-old seedlings were coppiced after a full year for establishment and growth. Sheep are able to digest the majority of seeds within the pods. However, for complete utilization by sheep, cattle, horses or swine, pods and seeds must be machine processed.

Apiculture: Flowers are very attractive to bees, which make honey from the nectar.

The specific gravity of the wood is 0.60 green, 0.67 oven-dry, and it is considered an excellent source of fuelwood.

Timber: The wood is strong, hard and durable, resistant to shock, and reddish-brown with attractive figuring; it is used locally for fence posts, pallets, crating, general construction, railroad ties and by woodworkers for making guitars.

Shade or shelter: G. triacanthos is hardy and drought tolerant; it can be grown in windbreaks with the added benefit of pod production.

Medicine: In Lesotho, fruit pulp is used for lung diseases. Powdered seed is used as snuff for head colds. Reported to be anodyne, mydriatic, narcotic, and experimentally oxytocic, G. triacanthos pods are a folk remedy for dyspepsia and measles, colds and fevers among the Indians of the USA; Delaware Indians used the bark for blood disorders and coughs. The bark tea treats whooping cough.

Gum or resin: The gum from the seeds has been suggested as an emulsifying substitute for acacia gum and tragacanth.

Ornamental: Its readiness to grow from seed, rapid growth, easy culture and extreme hardiness are among the commendable characters that make this tree popular for planting in gardens, parks or along highways. It has been widely planted as a replacement for American elm in North America and Canada with over 50 recognized cultivars. Budding can produce thornless trees with scionwood taken from the upper branches of selected cultivars. Thornless seedlings can be selected at a very early age (within 10 weeks of germination) for use as ornamental cultivars.

Intercropping: Widely spaced overstorey fodder trees (fodder orchard) can be planted for on-farm silvopastoral systems and should be compatible with a variety of forage, grain, vegetable, woody perennials or animals in the understorey.

Alcohol: A potable or energy alcohol can be made by fermenting the pulp.