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Plant Profile: Thornless Honey Locust (Gleditsia triacanthos var. inermis)

Locust Thornless honey Gleditsia triacanthos inermis leavesThis deciduous tree is native to parts of central United States where it often occupies bottomlands. The leaves are pinnately or bipinnately compound and the leaflets are small and so that raking is rarely necessary. The glossy bright green leaves appear late in the spring and turn bright yellow in the autumn before their early fall. The light shade of the canopy combined with the late appearance and early disappearance of the leaves facilitates the growing of grass beneath the tree. In late spring to early summer spikes of greenish yellow inconspicuous fragrant flowers are produced followed by large twisted brown to purple pods that can be a considerable litter problem. The short main trunk is gray-brown and develops plate-like patches separated by furrows. It is attractive especially in winter but may bear thorns that can be a hazard. Thornless Honey Locust is tolerant of drought, short term flooding, salt, compaction, and pollution so can be used in difficult sites including urban area such as parking lots and medium strips. Unfortunately, it is susceptible to a considerable number of pests and disease so should not be planted in mass.

Type: Deciduous tree

Outstanding Features: Tolerant of a wide variety of sites

Form: Oval or rounded; irregular silhouette; loose, open

Growth Rate: Rapid

locust thornless honey podsBloom: Small, greenish-yellow, fragrant flowers are borne in panicles in late spring to early summer. Large twisted green pods up to 12” long turn brown to purple in fall.

Size: 50-75’ H x 35-50’ W

Light: Full sun to part shade

Soil: Fertile, moist, well-drained but tolerates a wide range of soil.

Hardiness: Zones 3-8a

Care: Prune to one leader when young to develop good form and structure.

Pests and Diseases: Mimosa webworm, borers, pod gall midge, spider mites, bagworms, leafminers, aphids, and canker

Propagation: Seed; cultivars by bud grafting

Outstanding Selection: ’Moraine’ (fruitless, 40’ tall, good pest resistance and yellow fall color).

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