If you are a plant that must compete with other plants for the limited resources of light, moisture, and nutrients, how do you give yourself the upper hand? One strategy is to produce and release a toxin to inhibit the growth of other plants that would compete for the resources you need to survive. This approach, known as allelopathy, is utilized by many plants but most notably – for gardeners in this area – by the Black Walnut Tree (Juglans nigra).
Black Walnut trees produce a natural herbicide known as Juglone that will kill or stunt the growth of plants grown within its root zone. This toxin is released by all parts of the tree, including leaves, fruit, stems, and roots. Since the roots can extend 50-80 from the base of the tree, this creates a large zone that is off-limits for growing many plants.
While the Black Walnut tree is an attractive native tree that is a valuable food source for native wildlife, if your property is home to one of these trees you are familiar with the frustration of trying to garden in its vicinity.
Here is our list of plants that are tolerant of Juglone and can cohabitate with Black Walnut Trees.