Getting plants to grow under and around black walnut trees (Juglans nigra) is a problem. This is because the root bark gives off a toxin that is harmful to other plant roots. This adaptation may help these trees to secure a place in a crowded forest by keeping other trees from competing for soil nutrients. The soil beneath black walnuts also tends to be alkaline as well. The following list of plants have been found growing within the root spread of black walnut trees. These plants are only suggestions and we do not imply a 100% success rate with them. Remember to take care to plant away from the lateral roots of the walnut trees.