I understand redbud can be planted under black walnut. Can a weeping redbud work, knowing it is grafted on another type of tree, will the graft take the blackwalnut as well. If garden is on hill will this help with amount of toxin in soil. Thank you
Cercis canadensis ‘Covey’, sometimes referred to as Lavender Twist, is not affected by the allelopathic qualities of the Black Walnut Juglans nigra. According to the Missouri Botanical Gardens, this weeping cultivar is best grown in average, medium moisture, well-drained soil in full sun to part shade. The tree does not transplant well, so you want to be sure you are choosing a good location for your tree. This weeping cultivar has a dense umbrella-shaped crown with contorted stems and arching branches. It can either be staked to grow taller to approximately 8-10 feet tall, or if left alone may reach 5 feet.
The harmful effects of juglone on surrounding plants can depend on the soil and its moisture conditions. Good drainage may decrease responses to juglone, thus when planting near a black walnut tree enhancing soil drainage would be beneficial whether the garden is sloped or not.
For further information about what can grow with a black walnut, you may like to read a factsheet on our website found here: https://www.torontomastergardeners.ca/index.php/factsheet/juglone-and-black-walnut-a-toronto-master-gardeners-guide/.