Black Locust Tree Care Guide

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The Robinia pseudoacacia, or black locust tree, is hardy in USDA zones four through eight. In the spring, they are attractive thanks to their fragrant flowers, which are clusters of blooms that measure five-inches.

These flowers are attractive to honeybees, which make especially good honey from them. While growing black locust trees is easy, it is also worth knowing that it pays to be diligent when removing suckers.

Black locust trees are members of the legume family. As the spring blooms fade, they are replaced by pods, each of which boasts between four and eight seeds. Locust is particularly known for its ability to trap nitrogen from the air, using it to enrich the soil.

While the black locus may grow as tall as 80 feet, heights of between 30 and 50 feet are common. The canopy may spread as much as 30 feet. Thanks to irregular branches, this tree casts light shade, which means that plants requiring partial shade will thrive beneath this tree.

What You’ll Learn

Care Guide

Young black locus trees generally do best when planted in full sun or with a light amount of shade. Loose, well-drained soil is recommended, but most black locusts are hardy enough to survive in any type of soil.

Keep the soil around the tree moist during the first growing season. Water is less necessary in subsequent years. If the tree fails to thrive, consider using a fertilizer that contains phosphorus and potassium, as the black locust tree excels at taking nitrogen out of the air by itself. For instance, a 10-10-10 fertilizer might be ideal.

Unless you want to cultivate a forest of black locust trees, it will be necessary to regularly remove shoots from the root system.

Companion Plants

Choose shrubs that do well in full or partial shade to plant beneath the spreading branches of a black locust tree. Popular examples include azaleas, which are available in a wide variety of colors, and forsythia, which many people love because of its showy yellow display at the end of winter.

Other shrubbery options include inkberry, Japanese Andromeda, and rhododendron.

If you are looking for options for perennials that will do well in full or partial shade, then consider soapwort, which has the added advantages of being easy to grow and attractive to butterflies and bees. It’s even deer-resistant. Coral bells are another popular and colorful option that attract hummingbirds.

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The Green Pinky

About the author: Carley Miller is a horticultural expert at TheGreenPinky. She previously owned a landscaping business for 25 years and worked at a local garden center for 10 years.

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