What Are Allelopathic Trees: Effects on Tree Spacing 

By: Shelby McCullough| Published: November 14, 2022

Are your trees showing signs of disease or not growing as healthy as they should? Call McCullough Tree Service at 407-734-5854.

allelopathic trees

Many homeowners choose trees to plant based on their appearance and landscape goals, such as the desire to create shade. However, they may not realize they should not plant certain trees together — or even within the same vicinity. Some species are allelopathic trees, meaning they release harmful chemicals that can kill other nearby trees and plants.

Unless you’re familiar with these tree species, which include popular species like sugar maple and junipers, it’s easy to make mistakes that can affect landscape health. Our professional arborists at McCullough Tree Service keep up with the latest research published by academic presses and can help you select suitable trees. When you want to ensure existing allelopathic trees don’t harm new native tree seedlings or you’re planting new trees, our tree spacing guide can help.

Understanding the Allelopathic Effects of Trees

Allelopathic plants and trees are survivors. They release chemicals, either via different parts of the plants or in decomposition, that harm other plants. The chemicals destroy nearby plants by stopping their growth. For example, they might stunt seedling growth by preventing root development or access to nutrients. 

One of the best examples of an allelopathic tree is the black walnut. This tree produces a chemical called juglone, which affects plants like pine and apple trees, azaleas, tomatoes, and peppers. However, many plants tolerate juglone and grow without any issue near black walnut trees. 

Allelopathic trees typically only affect certain species. This makes it especially important to know which trees you have in your yard and how allelopathic chemicals could affect them. Knowing how your trees co-exist ensures you don’t inadvertently plant allelopathic trees too close to those they can harm. 

Spacing of Allelopathic Trees

With proper spacing, it’s possible to plant allelopathic trees and their victims in the same yard. Plant them as far apart as possible, keeping in mind that the soil can significantly impact how much damage the chemicals can do.

Generally, heavier soils without good drainage hold the toxins from allelopathic trees longer, increasing the impact on nearby plants. In contrast, well-drained soils help move allelopathic chemicals below the roots, limiting the effects. Microorganisms in healthy soil can also help prevent allelopathic effects, as they can help eliminate or convert toxins into less harmful substances. 

Allelopathy is not always a bad thing, either. Scientists suspect that it may help forests restore themselves after disasters, as natural toxins can help prevent invasive weeds from choking out native tree seedlings. Depending on the specific plants the toxins affect, allelopathic trees can actually help your landscape stay healthy. 

Call McCullough Tree Service for Help with Allelopathic Trees 

If you suspect that you have a problem with allelopathic plants killing your trees or have signs of an issue like a mushroom growing on a tree, call the leading tree experts in Orlando, FL, for help. Our McCullough Tree Service team can help identify the problem and provide practical solutions to help protect your landscape. Call us today at 407-734-5854 to schedule an appointment.

Shelby McCullough

About The Author: Shelby McCullough

With over two decades of experience in the tree industry, Shelby McCullough is a highly skilled certified arborist and the proprietor of McCullough Tree Service. His unparalleled expertise and profound understanding of trees set him apart in his field.