Gleditsia triacanthos - Thornless Honeylocust

Gleditsia triacanthos, more commonly known as the Honeylocust, is a large thorny tree, related to Acacias and Mimosas. Its deciduous foliage, shiny and finely cut like that of the Mimosa, is tender green from spring to summer, turning deep yellow in autumn. Its trunk, branches, and twigs are covered in very long sharp thorns. With its airy and majestic habit, it provides a light shade, very pleasant in summer. Beautiful as a standalone tree, this unique specimen will adapt to any type of soil, and its good hardiness will allow it to acclimate throughout the UK.

Gleditsia triacanthos is a tree of the Fabaceae family, related to the carob tree, native to the eastern and central United States (from Nebraska, through Pennsylvania to Texas). Its long thorns have earned it the name "Christ's Thorn". Very resistant and sharp, they were once used to make nails and needles. As an ornamental tree and utility plant, the Honeylocust has hard and dense reddish-brown wood, locally used for making poles, railroad ties, and also appreciated in cabinetmaking. Its foliage, rich in proteins, is excellent fodder for livestock.

The Honeylocust has a rapid growth, especially on moist soil. Its silhouette is taller than wide, airy towards the top, and its vegetation is arranged in a 'drapery' fashion. It will reach approximately 20m (65ft 7in) in height with a spread of 15m. The foliage appears late, at the end of spring. The large leaves, finely cut into small leaflets, are alternate and pinnately compound, measuring between 12 and 30cm (4.7 and 11.8in). The tender green foliage has a shiny texture that plays beautifully with light, even when seen through. The straight and bare trunk has a beautiful dark bark with deep fissures. Just like the branches and twigs, it is adorned with long reddish-brown sharp thorns. This tree is dioecious (there are male and female individuals) and its discreet summer flowering is highly attractive to bees. Only the female trees bear mahogany to brown, flattened pods, 20 to 40cm (7.9 to 15.7in) long, persistent in winter, with sweet and edible pulp. Young plants need protection from severe cold, but an adult tree can withstand temperatures well below -15°C (5 °F). This tree has a deep taproot system that requires a soil of considerable depth.

One might wonder why the Honeylocust and its varieties are not more commonly planted in the UK, which seems to only welcome the Mimosa in its gardens, despite it being less hardy and not easier to cultivate. This is probably due to its insignificant flowering, which is largely compensated by the splendour of its foliage, but also because of its threatening thorns. It is best planted as a standalone tree, in a spacious garden, where it will provide light shade without preventing other plants from growing around its base. It should be avoided near houses, paths, or roads, due to its thorns that can cause injuries or even puncture passing vehicles' tires. It is possible to remove the thorns using long-handled pruners, taking the necessary precautions of course. This highly adaptable tree, if it thrives in rich and moist, even poorly drained soil, ultimately tolerates dry, poor, and calcareous soils once it is well established.