Gleditsia triacanthos f. inermis 'Impcole' IMPERIAL
Common Name: imperial honey locust | Type: Tree
Family: Fabaceae | Zone: 3 to 8
Height: 30.00 to 40.00 feet | Spread: 25.00 to 35.00 feet
Bloom Time: May to June | Bloom Description: Greenish yellow to greenish white
Sun: Full sun | Water: Medium
Maintenance: Medium | Suggested Use: Street Tree
Flower: Insignificant | Leaf: Good Fall
Fruit: Showy | Tolerate: Deer, Drought, Clay Soil, Black Walnut, Air Pollution
Culture Best grown in organically rich, moist, well-drained soils in full sun. Tolerant of a wide range of soils. Also tolerant of wind, high summer heat, drought and saline conditions.
Gleditsia triacanthos, commonly called honey locust, is native from Pennsylvania to Iowa south to Georgia and Texas. It typically grows 60-80’ (less frequently to 120’) tall with a rounded spreading crown. Trunk and branches have stout thorns (to 3” long) that are solitary or three-branched. Inconspicuous, greenish yellow to greenish white flowers appear in racemes in late spring (May-June in St. Louis). Flowers are followed by long, twisted and flattened, dark purplish-brown seedpods (to 18” long) which mature in late summer and persist well into winter. Seedpods contain, in addition to seeds, a sweet gummy substance that gives honey locust its common name. Species plants are generally not sold in commerce today because the thorns and seedpods are considered to be significant liabilities.
Forma inermis is a thornless variety (inermis from Latin means unarmed) that occurs naturally in the wild. It grows to the same height as the thorny species plants. Cultivars of G. triacanthos which are sold in commerce today are all cultivars of f. inermis (no thorns and in many cases no seedpods make them preferred landscape plants). Pinnate to bipinnate dark green leaves with ovate leaflets (1/2” to 1 1/2” long) cast a sun-dappled shade. Leaves turn an attractive yellow in fall.
Genus name honors Johann Gottlieb Gleditsch (1714-1786), director of the Botanical Garden, Berlin.
Specific epithet comes from the Greek acantha meaning thorn and tri meaning three in reference to the three-branched thorns on species plants.
'Impcole' is commonly sold in commerce under the trade name of IMPERIAL. It is a thornless and nearly seedless variety that typically matures in a rounded compact form to 30-40' tall. It features spreading branches and often lacks a single central trunk. Pinnate to bipinnate dark green leaves with ovate leaflets (1/2” to 1 1/2” long) cast a sun-dappled shade. Leaves turn an attractive yellow in fall. U.S. Plant Patent PP1,605 was issued on May 21, 1957.
Problems Honey locust is susceptible to a large number of potential disease problems, including leaf spot, canker, witches’ broom, powdery mildew and rust. Borers and webworms are common insect problems in some areas. Bagworms, plant bug, leafhopper and leaf miner may appear. Watch for spider mites.