866 Gleditsia triacanthosCommon Names: honeylocust, thornless honeylocust Family: Fabaceae (bean Family)
Honeylocust is a medium size deciduous tree with black bark, zigzag twigs and pinnately compound leaves. Its most distinctive feature is its armament. The trunk and larger branches bristle with stout, rigid, branched thorns 7-20 in (17.8-50.8 cm) long, which grow from deep within the wood. They are formidable indeed. Most of the cultivars have been selected from a thornless form which occurs sporadically in nature: Gleditsia triacanthos f. inermis.
Honeylocust usually stands around 40-80 ft (12.2-24.4 m) tall and has an open plumelike crown of fine-textured foliage that spreads 20-30 ft (6.1-9.1 m) across. Really huge specimens in optimal habitat along the Ohio or Mississippi Rivers can be 140 ft (42.7 m) tall and have trunks 6 ft (1.8 m) in diameter. The tallest of three honeylocusts tied for National Champion is an open grown specimen in Michigan, 116 ft (35.4 m) tall with a trunk diameter of 5.3 ft (1.6 m) and a crown spread of 104 ft (31.7 m). Honeylocust leaves are compound and often doubly compound, 7-8 in (17.8-20.3 cm) long, and divided into a hundred or more 1 in (2.5 cm) oval leaflets. The fragrant greenish yellow flowers hang in small, inconspicuous clusters in early summer. Honeylocust is in the legume family, and its seeds are borne in pods. These are dark purplish brown, flat and corkscrew twisted, 10-18 in (25-45.7 cm) long and about 1 in (2.5 cm) wide. The pods frequently persist on the tree after leaf fall into early winter. The seeds resemble oval bean seeds and are surrounded within the pods by a sweet and juicy pulp.
Many thornless cultivars are available, selected for sterility (no litter from the seed pods), foliage color, form and size. 'Moraine' was the first cultivar to be patented; it is nearly podless, relatively resistant to mimosa webworm, and grows to 50 ft (15.2 m) tall. 'Elegantissima' has a dense shrubby form and is smaller, to 25 ft (7.6 m) tall. 'Imperial' has a spreading form, 30 ft (9.1 m) tall and 30 ft (9.1 m) wide, and produces few seed pods. 'Shademaster' is taller and narrower and almost podless. 'Sunburst' leaves are yellow when they first unfold and the tree is reportedly podless. 'Pendula' or 'Bujotii' is shrubby with slender, weeping branches.
Mainly a tree of the flood plains along the Mississippi River and its major tributaries, honeylocust, Gleditsia triacanthos, ranges from Iowa south to East Texas, thence east to western Alabama and north to western Pennsylvania. Honeylocust is a characteristic tree on the ridges and swells within overflow swamps. It is never particularly abundant, and usually grows singly or in small groups in association with other trees of the bottomlands such as red maple (Acer rubrum ), blackgum (Nyssa sylvatica ), pecan (Carya illinoinensis), boxelder (Acer negundo), persimmon (Diospyros virginiana), overcup oak (Quercus lyrata), and various ashes (Fraxinus spp.). The thornless form, Gleditsia f. inermis, occurs occasionally throughout the range of the species.
CultureHoneylocust is a fast growing tree which is very tolerant of alkaline soils, salty soils and urban conditions, including air pollution. Young specimens can put on 2-3 ft (0.6-0.9 m) of growth per year. Unlike most legumes, honeylocust does not have nitrogen fixing nodules on its roots, and therefore must obtain this element from nitrates in the soil. The tree is susceptible to several insects and diseases and periodic spraying is often necessary. Light: Honeylocust needs full sun. Lower limbs die if shaded but may remain on the trunk for years. Moisture: Although honeylocust grows naturally in swamps it is surprisingly tolerant of drought. Hardiness: USDA Zones 4 - 9. The species and the cultivars vary in cold hardiness, and some may be hardy to zone 3B. Most, if not all, of the cultivars apparently were selected from northern stock and do poorly in the heat and humidity of the American Southeast. Propagation: Sow seeds in fall (scarify first) and leave outdoors for spring germination. The thornless cultivars of honeylocust are usually propagated by budding or grafting onto seedlings of the species. About 60% of seeds from thornless honeylocust produce thornless seedlings. Honeylocust transplants easily.
Honeylocusts, especially the thornless cultivars, are popular ornamental, shade, street and specimen trees. They have a thin, lacy canopy which permits grass to grow right up to the trunk. They are a good tree for use where you want to see beyond and through the canopy. Their salt tolerance makes them ideal street trees for cities that use deicing salts. Owing to its drought tolerance and wind resistance, the typical species is much used for shelterbelt planting on the American Great Plains. Choose nonfruiting cultivars to avoid the litter of fallen seed pods, and thornless cultivars to avoid impaling innocent bystanders.
The sweet smelling flowers are much favored by bees and the juicy pulp between the seeds within the pods is relished by cattle and wildlife. In fact the nutritious pods are a valuable stock food in some areas, and cattle are turned loose into the swamps when the honeylocust pods are ripe. The wood is very hard, very heavy, and resistant to decay. It is used occasionally for furniture, fence posts and railroad ties, but its scarcity limits widespread use.
Thornless honeylocust is an attractive and picturesque landscape tree but now overused throughout most of its adaptable range. It was formerly planted in cities to replace American elms (Ulmus americana) that died from Dutch elm disease, but now the honeylocusts too are dying from various insects (especially mimosa webworm and honeylocust borer) and disease. Thornless honeylocust still has a place in the landscape as an individual shade or specimen tree, but probably should not be used in mass plantings.
The typical species, with its dangerously sharp spines, is a threat to life and limb, as well as your homeowner's insurance policy.
Steve Christman 11/22/00; updated 10/22/03, 7/14/04, 9/9/04, 8/28/12