Juglans Family (Walnuts) The Black Walnut Neighbourhood As some of you already know, many plants simply do not grow well when planted close to a walnut tree. The roots of both the black and English walnut as well as the butternut give off a toxic substance known as juglone which eliminates their competition. It will kill most evergreens, as well as some fruit trees and a number of vegetables. Most grasses seem not to mind, and some plants actually seem to thrive. The following is a short list of some of the best neighbors for a walnut tree: Black raspberries, Grapes, Rugosa roses, High bush cranberries, Black locust, Goumi, Persimmons, Paw paws, Mulberries, Currants, Elderberries, Sweet corn, Beans & Onions. Some of the poorest choices include: Apples, Pears, Blackberries, Tomatoes & Alfalfa. Bareroot trees