Gleditsia triacanthos (Honey Locust)
|Also known as:|
|Life cycle:||perennial woody|
|Habitat:||sun; moist soil; rich woods, urban landscapes|
|Bloom season:||May - June|
|Plant height:||50 to 80 feet|
|Wetland Indicator Status:||GP: FACU MW: FACU NCNE: FAC|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Elongated racemes 2 to 5 inches long from leaf axils on young branches, with separate male and female flowers usually on separate trees or on separate branches of same tree, though some flowers can be perfect (having both male and female parts). Flowers are greenish yellow, 1/8 to ¼ inch across. Male flowers are densely packed in the cluster and have 4 or 5 petals with 5 or 7 stamens.
Female flowers are more loosely clustered and have a single stout, pale pistil with a greenish cap; perfect flowers have stamens surrounding the pistil. For both sexes, the calyx holding the flower is 5-lobed, green and hairy. Flowers are fragrant.
Leaves and bark:
Leaves are alternate and once or twice compound, sometimes both types on the same branch. Once compound leaves are 4 to 7 inches long with 6 to 12 pairs of leaflets, typically in clusters on older lateral branches. Twice compound leaves are up to 12 inches long with up to 150 leaflets. Leaflets are mostly lance-elliptic, up to 1¼ inches long, toothless or scalloped along the edges, and once-compound leaflets about twice as large as twice-compound leaflets. Surfaces are smooth or sparsely hairy, or just hairy along the midvein and stalks. The upper surface darker than the lower surface. Fall color is a deep gold.
New twigs are green and finely hairy, becoming reddish or greenish brown, smooth and shiny with small brownish lenticels (pores) and swollen nodes. Branches become dull, dark gray to nearly black, rough textured from the lenticels.
Fruit is a long, flattened pod up to 15 inches long and 1¼ inches wide, drying dark purplish brown and very twisted, the bean-like seeds inside dark brown and shiny, very hard, flattened kidney-shaped, about 1/3 inch long.
Minnesota sits at the very northwest edge of Honey Locust's North American range with a sole record collected in Houston county in 1899. That collection site is now flooded by the backwaters of Lock and Dam #8 and the native species is likely extinct in the state. However, it is a popular urban tree and has been widely planted throughout much of the state. Trees found growing wild in rural woodlots and shelter belts are likely naturalized from these plantings. Honey Locust is tolerant of a wide range of both wetter and drier sites and there are many cultivars of this species, selected on foliage color (red and yellow), male trees that produce no fruit and well as lacking thorns (var. inermis). Its form can be widely variable as well, growing tall and round topped with ascending branches or often with lower spreading branches on limbs that have diverged from the trunk, low on the tree. The only tree it might be confused with is the Black Locust (Robinia pseudoacacia). It however has only once compound leaves with leaflets that are larger and more oval with round tips, its thorns are short spines, about ¾ inch long in pairs at the nodes, the flowers are large showy clusters of white pea-like blossoms and its bean pod is much smaller, only 3 to 4 inches long and not twisted.
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- Honey Locust tree in fall color
- thornless Honey Locust tree in a boulevard planting
- younger trunk, and its thorns
- upper branches are thorny, too
- scan of once-compound leaf
- cluster of once-compound leaves
- twice-compound leaves emerging in spring
- flowering branches
Photos courtesy Peter M. Dziuk taken at numerous urban locations in the Twin Cities Metro area, a Washington County shelterbelt, and in Illinois.
Have you seen this plant in Minnesota, or have any other comments about it?