Juglans nigra, commonly known as black walnut, is the largest of the twenty species of Juglans native to the United States. It easily grows to a height of 100 feet; its strong, straight trunk and magnificent canopy enhance most any landscape that has an appropriate scale for the trees massive size.
It is prized by the high-end furniture market because of its uniformity, durability and the luxurious chocolate-brown color of its heartwood. Many landowners, who have a few acres to spare, are planting genetically superior black walnut trees as an investment which will mature in 25 to 30 years.
Horticulturists discovered that certain plants did not do well, while some withered and died, when planted close to or underneath the canopy of black walnut trees. Black walnut trees secrete a biochemical substance known as Juglone. These secretions sometimes drip from the leaves down onto plants and ground below and leaches out from the roots below ground as well. The process is known as allelopathy.
Though Juglone is a poison to many plant varieties, making it difficult in planting under black walnut trees. However, there is still a large number of shrubs and perennials that can be safely planted under the canopy or near black walnut trees that are resistant to the effects of Juglone.
Visit Greenwood’s page on Planting under Black Walnut trees for a selection of plant varieties that will grow under the canopy of the black walnut trees.
More info on plants that will and will not grow under or near black walnut trees:
Ohio State University Extension Black Walnut Tree Fact Sheet
West Virginia University Extension Service
- Homegrown style: planting a family tree of tradition (telegraph.co.uk)
- Walnuts in malakand division (tahirkatlang.wordpress.com)