Common Name: Honey Locust

General Information

Gleditsia triacanthos is a deciduous tree with an open, spreading crown; it usually grows around 15 - 30 metres tall, but has been known to reach more than 40 metres in the wild. The bole is usually somewhat short, and often divided near the ground, it can be 150 - 180cm in diameter; both it and the branches are more or less armed with stout, sharp, branched spines 8 - 30cm long. The plant produces suckers and can form dense, impenetrable thickets[, , ].
A multi-purpose tree, it is harvested from the wild for local use as a food, medicine and source of materials. The honey locust is often cultivated in warm temperate zones for its edible seeds and seedpods, and is often sold in local markets[, ]. It is used in soil reclamation projects, as a barrier hedge, and is also sometimes grown as an ornamental. Unarmed forms of the tree are used in avenue and roadside plantings[].
This species is a thorny, woody leguminous tree that has a tendency to be an aggressive colonizer. Root suckers and abundant seed production gives an ability to rapidly form dense, impenetrable stands. It is considered to be an invasive weed in Australia, especially in Queensland, and in its native USA, it is known for invading pastures and prairie. It appears to require warm (temperate or mediterranean) climates with moist (moist semi-arid to sub-humid) conditions to become invasive, though actual requirements are far from clear, and human influences are also probable[].

Known Hazards

The plant contains potentially toxic compounds[].

Botanical References

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Range

Eastern N. America - southeastern South Dakota to Pennsylvania, south to Texas and Georgia. Occasionally naturalized in C. and S. Europe

Habitat

Usually growing singly, though sometimes forming almost pure woods, on borders of streams, in rich woods, in moist fertile soils, sometimes on dry sterile gravelly hills; usually at elevations up to 750 metres, occasionally to 1,500 metres[, , ].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	20.00 m
Growth Rate	Medium
Pollinators	Insects
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Gleditsia triacanthos is native from the cold temperate to the subtropical zones of N. America, though it has also been successfully cultivated in tropical areas[]. It requires hot summers if it is to fruit well, but will generally thrives, even if it does not fruit, in areas with cool summers. It is very cold-hardy, with older trees being able to tolerate temperatures down to around -35°c when fully dormant. The tree has a habit though, especially when young, of producing new growth until quite late in the season. Especially in areas where the summers are not hot, this new growth will not ripen fully and will be liable to be cut back by the cold in the winter. Older plants tend to lose this habit. Generally, the dormant plant should be considered to only be hardy to about -5°c when young, especially if growing in areas with cooler summers[]. It grows best in areas where annual daytime temperatures are within the range 26 - 38°c, but can tolerate 6 - 40°c[]. When dormant, the plant can survive temperatures down to about -34°c, but young growth is more tender and can be severely damaged at -1°c[]. It prefers a mean annual rainfall in the range 700 - 1,500mm, but tolerates 500 - 1,800mm[].
Requires a sunny position[]. Succeeds in most soils, acid or strongly alkaline[, ], so long as they are well-drained[]. Trees have a wide-ranging, deep root system and tolerate drought once established[]. Tolerant of atmospheric pollution[]. Salt tolerant[, ]. The plant is wind-firm[].Prefers a pH in the range of 5.5 - 8, but tolerates 4.5 - 9[, ].
Honey locust is often cultivated in warm temperate zones for its edible seeds and seedpods[, ], trees start to bear when about 10 years old and produce commercial crops for about 100 years[]. Wild trees seldom live longer than 120 years[].
The optimum yield of dry pods is 450 kg per year per tree[].
There are some named varieties[]. The sub-species nana produced lots of viable seed in the hot summer of 1989 at Kew in England (hardiness zone 7 - 8)[], it also had a very good crop in 1994, 1996 and in 1999[]. The sub-species inermis had a very good crop of pods in the autumn of 1996[]. 'Ashworth' has pods with a very sweet pulp that has a melon-like flavour[].
The wide-ranging, deep root system of this plant can extend into and block sewers and drains[].
The plant is functionally dioecious, both male and female forms need to be grown if fruits and seed are required[]. The flowers have a pleasing scent[].
A very ornamental tree[], the flowers are very attractive to bees[, ].
Trees have a light canopy, they come into leaf late and lose their leaves early[] making them an excellent canopy tree for a woodland garden.
Plants in this genus are notably resistant to honey fungus[].
Unlike most plants in this family, honey locusts do not fix atmospheric nitrogen[, ].

Edible Uses

Seed - raw or cooked. It can contain up to 30% sugar[]. Young seeds taste like raw peas[]. Seeds are not always borne in maritime regions because the tree prefers long hot summers[]. The oval seeds are about 8mm long[]. They contain 10.6 - 24.1% protein, 0.8 - 4.3% fat, 84.7% carbohydrate, 21.1% fibre, 4% ash, 280mg calcium and 320mg phosphorus per 100g[].

The seeds have been roasted and used as a coffee substitute[, ].

Seedpods - the pulp of immature pods is sweet and can be eaten raw or made into sugar[, , , ]. The pulp in older pods turns bitter[]. The dark shining brown, scimitar-shaped seedpods are up to 40cm long and 4cm wide[, ].
The tender young seedpods can be cooked and eaten[].

A sweet, pleasant tasting drink can be made from the seed pods[].
The seed pulp has been used to make a drink[]. It has been fermented to make an alcoholic beverage[].

Medicinal

The seedpods have been made into a tea for the treatment of indigestion, measles, catarrh etc[, ]. The juice of the pods is antiseptic[]. The pods have been seen as a good antidote for children's complaints[].

An infusion of the bark has been drunk and used as a wash in the treatment of dyspepsia[]. It has also been used in the treatment of whooping cough, measles, smallpox etc[].

The twigs and the leaves contain the alkaloids gleditschine and stenocarpine[]. Stenocarpine has been used as a local anaesthetic whilst gleditschine causes stupor and loss of reflex activity[].
Current research is examining the leaves as a potential source of anticancer compounds[].
The alcoholic extract of the fruits of the honey locust, after elimination of tannin, considerably retarded the growth, up to 63% of Ehrlich mouse carcinoma[]. However, the cytotoxicity of the extract was quite high and the animals, besides losing weight, showed dystrophic changes in their liver and spleen[]. The alcoholic extract of the fruit exerted moderate oncostatic activity against sarcoma 180 and Ehrlich carcinoma at the total dose 350 mg/kg/body weight/mouse. Weight loss was considerable[].

Agroforestry Uses:

Honey locust is a natural pioneer species, invading pasture land and open prairies, especially in drier regions. It is considered a weed by cattle ranchers, but is an excellent pioneer species for restoring native woodland and also for establishing a woodland garden. The tree is shade-intolerant and so is likely to eventually be overtopped by successional trees and then die out because of lack of sun[].[, ].
When planted close together and severely pruned, this species forms good windbreaks and hedges. With their usually very spiny trunks and branches, the hedge becomes a dense, spiny and very effective intruder-proof barrier, and with its ability to fix atmospheric nitrogen, it also enriches the soil[, ].
The tree has often been planted in erosion control projects and has also been used for land reclamation projects on mining waste[, ].

Other Uses

The gum from the seeds has been suggested as an emulsifying substitute for acacia and tragacanth[].

An extract of the seed is used as an ingredient in commercial cosmetic preparations as a hair conditioner[].
An extract of the wood is used as an ingredient in commercial cosmetic preparations as a skin conditioner[].

The heartwood contains 4 - 4.8% tannin[].

The seedpods are being fermented for ethanol production in studies to explore the feasibility of biomass fuels[].

The heartwood is light red to reddish brown; it is demarcated from the wide band of yellowish sapwood. Texture is moderately coarse, with a straight to irregular grain; there is no characteristic odour or taste; lustre is high. The wood is very heavy, very hard, tough, strong, very shock-resistant, durable in contact with the soil. It does not shrink much in drying. The wood is not easy to work, splits rather easily and does not glue well, but finishes smoothly and takes a high polish. It is used primarily for making fence posts and rails, general construction, furniture, interior trim[, , , , , , , ].
The wood is an excellent fuel and can be used to make charcoal[].

Propagation

Seed - pre-soak for 24 hours in warm water and then sow in spring in a greenhouse[]. The seed should have swollen up, in which case it can be sown, if it has not swollen then soak it for another 24 hours in warm water. If this does not work then file away some of the seed coat but be careful not to damage the embryo[]. Further soaking should then cause the seed to swell. One it has swollen, the seed should germinate within 2 - 4 weeks at 20°c. As soon as they are large enough to handle, prick the seedlings out into individual deep pots and plant them out into their permanent positions in the summer. Give the plants some protection from the cold for their first few winters outdoors.