Black walnut trees are majestic trees valued for their fruit and for their timber. However, black walnut trees can wreak havoc on your garden. Every part of the black walnut tree produces a toxic substance called juglone. There are many plants--such as tomatoes, peppers, blueberries and apples--which will yellow, shrivel and die if they are planted near a black walnut tree. Additionally, many shrubs, flowers and grasses are equally sensitive and can make landscaping around your black walnut difficult. To successfully plant near a black walnut tree, you must be aware of which plants are sensitive and which are tolerant.
Keep the garden soil in the area around your black walnut well-draining and rich in organic matter by regularly adding compost and by using mulch.
Pick up any fallen leaves, buds or nuts as soon as they litter the ground.
Choose trees, shrubs, flowers and other plants which are not effected by the juglone of black walnut trees when landscaping or gardening in the proximity of the tree.
Avoid planting any plants which are sensitive to juglone under the canopy of the tree or within reach of its root system.
Use raised beds or a barrier such as a rock wall or driveway to separate your garden from your black walnut tree if you are unable to plant out of the vicinity of the tree.