Answer: Black walnut tree roots exude juglone which inhibits growth in susceptible plants. Unfortunately, plants in the nightshade family (solanaceae) are particularly susceptible: your tomatoes, peppers, eggplants and potatoes in particular will either die or be stunted. (Apples, raspberries, blueberries, asparagus and some of the cole crops are also among those reported sensitive.) The "safe distance" from the tree is determined by the size of the tree. You need to locate the vegetable garden outside the tree's root zone. For a mature tree, the safe distance can easily require a 50 or 60 foot radius away from the trunk. In younger trees, the root zone could conceivably reach twice as far as the height of the tree. The toxin also leaches from the leaves and nuts, so you will need to remove these if they fall or blow into your garden.
Q&A Library Searching Tips