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


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.

Noteworthy Characteristics

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. The 4-8" long leaves are bipinnately compound and made up of small (up to 1" long), elliptic to lanceolate leaflets. The leaves turn bright yellow in the fall. 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 numerous flattened, round seeds surrounded by a sweet, sticky pulp. 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 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. The infraspecific epithet inermis comes from Latin and means "unarmored" or "toothless" in reference to the lack of spines in this form.

'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.


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.


A thornless and nearly seedless form that is recommended for lawns and streets.