Gleditsia triacanthos L.
Family: Fabaceae (was Caesalpiniaceae)Names:
A small deciduous tree to 10 m tall with stout spines on the stem, long pods and alternate pinnate or bipinnate leaves. Male and bisexual trees.
150-200 mm long. Alternate. Pinnate with 5-15 pairs of pinnae or bipinnate with 12-30 pinnules on each pinnae. Both types may be on the same plant.
Leaflets are oval and mainly 10-35 mm long x 5-12 mm wide with a few teeth on the edges. The rachis (central stalk of the leaf) is hairy.
Stipules - Small.
Petiole - Hairy. 30-50 mm long.
Blade of leaflets - Base tapered, sides with a few teeth, tip rounded.
Stems:To 10 m tall. Stems and branches have stout, simple or branched spines that are 20-100 mm long. Some cultivars are spineless.
Flower head:Raceme is 50-100 mm long with short golden hairs.
Flowers:Greenish yellow. Axillary. Bisexual. On stalks (pedicellate).
Ovary - subsessile. Short style with a large terminal stigma.
Calyx - 3-4 mm long.
Petals - Greenish yellow. 4-6 mm long.
Stamens - 6-10. Free.
Fruit:Dark brown, slightly curved pod, that doesn't open or fall at maturity (indehiscent). 150-400 mm long x 30-40 mm wide, flattened oblong and somewhat leathery with15-25 transverse seeds. The pod is somewhat pulpy inside.
Seeds:About 10 mm long. Flat. Brownish.
Seed weight = 160 mg (110-260 mg) (Bonner et al., 1974).
Roots:Sucker when damaged.
Key Characters:Pinnate or bipinnate leaves.
Thorny stems on most cultivars.
Biology:Grafted trees are usually used for commercial purposes.
Life cycle:The pods are initially green and ripen to deep brown in autumn and persist until winter. Seed bearing starts from 5-10 years of age.
Physiology:Don't tolerate shade.
Reproduction:By seed and suckering.
Flowering times:Spring after new leaves have formed. Fruit ripens in autumn.
Seed Biology and Germination:Seeds need treatment with boiling water for good germination. Put 1 L seed in 3 L of nearly boiling water (900C) and allow to cool or remove them if they start to swell. Seed must be sown promptly and cannot be stored.
Soaking in concentrated sulphuric acid is more effective than the boiling water treatment (soaking times vary from 1-2 hours depending on the seed lot)
Seeds can be removed from the pods by hand flailing or mechanical threshing.
Seed can be stored in sealed containers at 0 - 70C for several years.
The germination test is a constant temperature of 200C for 21 days. Alternating temperatures 20/300C and light have also been used (Bonner et al., 1974).
For producing nursery stock plant in rows 10 cm apart with a seed every 4 cm. Seedlings will be ready for transplanting in about a year.
Hybridises with other Gleditsia species e.g. Texas Honey Locust (Gleditsia X texana).
Allelopathy:Population Dynamics and Dispersal:
Claims of 210 kg pods per tree when in cultivation but 100 kg/tree is more likely.
Origin and History:North America. First cultivated in the USA in 1700.
Distribution:NSW, QLD, WA.
Courtesy Australia's Virtual Herbarium.
Requires 500 mm rainfall or more.
Ornamental shade tree and shelterbelt. Timber for furniture but mainly for fence posts and sleepers (Bonner et al., 1974). Stock feed with claims of 16% protein and 60% carbohydrate in the pods. Opossums eat the green fruit.
Detrimental:May naturalise to become an environmental weed.
Suckers readily from cut roots.
Toxicity:Not recorded as toxic
Noxious weed of Queensland.
Management and Control:Cattle tend to debark them in spring.
Parkinsonia or Jerusalem Thorn (Parkinsonia aculeata) has much smaller leaflets.
Royal Poinciana (Delonix regia) has no thorns.
Senna (Senna spp.) has no thorns.
Plants of similar appearance:African Boxthorn (Lycium ferocissimum)
Black Locust (Pseudoacacia spp.)
References:Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).
Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume 2. P 313. Diagram.
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P
Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #450.1.
Randall, J.M. and Marinelli, J. (1996) Invasive Plants. (Brooklyn Botanic Gardens Inc. Brooklyn). P. Photo.
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