Thornless Honeylocust

Gleditsia triacanthos

Honeylocust trees mature quickly to 50-75′ x 40′ with a round canopy. They prefer medium soil moisture, but are a very common street and yard tree due to drought tolerance, pollution and compacted soils. It is ideal for parking lot medians as it handles heat and radiant heat very well. The natural, thorned variety has long and nasty thorns as well as messy, large and leathery seed pods. They are commonly found in wooded areas and old parks.

Common Problems

Environmental

Must be pruned to a single stem so as to avoid multi trunks. Branch spacing needs to be established otherwise the tree will suffer breakage as it matures (the ’Skyline’ cultivar is an exception). Surface roots are common and can be a problem if damaged from lawnmowers or root cutting for sidewalk or curb repairs.

Diseases

Canker causing fungi can be a serious problem but typically only attack stressed trees. Watering and fertilizing is helpful as a preventative measure. Watering should not be frequent and light as it promotes thyronectria (a canker fungi). Some leaf fungi are common, but hardly a problem meriting control.

Pests

Borers can be a serious problem but typically only affect stressed trees. Honeylocust Plant Bug is a very common problem which should be treated if occurring more than 1 year in a row. Honeylocust Podgall Midge is also a semi-serious issue if persisting more than one season and should be treated as it inhibits leaf development during the spring. They are often found along with plant bug, which usually feasts faster and more furious, resulting in a suppression of Podgall Midge populations. There are a variety of Aphids that attack the leaves of Honeylocusts which should be controlled. Spider Mites will attack the leaves turning them golden in the heat of the summer and should be controlled. Leaf Miners are a problem but uncommon in Colorado. Imidacloprid (Merit) treatments that are used to control several of the leaf eaters mentioned above often brings on more severe late summer attacks of the honeylocust spider mite. Trees should be monitored for this in August.

Cultivars

There a few cultivars available like ‘Skyline’ and ‘Sunburst’. In particular, the ‘Sunburst’ cultivar is very popular.

History and Use

This tree was not a popular selection because of its numerous, needle-sharp and massive thorns that defended it against casual climbing or cutting. Then, at the beginning of the 1900’s, while walking among the suburban woodlands of New York City, a man discovered and propagated the natural thornless hybrid that is so widely planted today.

Native Americans used the seed pulp for sweet foods. It can also be fermented for making beer. The wood is very hard and attractive. Locally it is salvaged and used in furniture. It can also be used outdoors as it is rot resistant.