Hi Dave - I have read your two-volume Edible Forest Gardens and am using it to help me design. My question is about the allelopathy of black walnut. Is there any validity to the claims that some plants will help to form a "buffer zone" around black walnut that will impede the spread of juglone beyond the buffer zone? I have read that hackberry, and white mulberry will do this. Another sub-question has to do with hackberry. Does the juglone tolerance differ between the local hackberry, Celtis occidentalis, commonly called northern hackberry, and the more southern hackberry, Celtis laevigata, commonly called sugarberry?
Looking at various lists of plants with juglone susceptibility and tolerance that are available on the internet, it is clear that some lists are just copies of others. The lists are confusing in that some plants are listed in some as tolerant and in other lists as susceptible. I gather that the lists have been compiled through observation and that variability of tolerance/susceptibility can come from 1) different varieties of the same species, 2) distance from the black walnut, 3) soil conditions--poorly drained soil creates more susceptibility. To help with this I have compiled for my own use a combined list showing what each list says about plants native to my area, Peterborough, Ontario. But hackberry is one of the plants that is listed as both susceptible and tolerant, and even buffer-zone forming, and the difference between the northern and southern species isn't clarified anywhere that I can find.
I wonder if you have anything you can add that would help my designing--the tree is on my neighbor's property immediately adjacent to my garden, and the range of the roots is listed as somewhere from 50' past the dripline to two tree heights past the dripline, so I definitely need to learn how to exist in harmony with this tree.
Thanks.
