Exciting times. Dug 150 holes last fall. Planning to plant 150 trees and bushes for a mini food forest.
I'm in zone 5a.
I was wondering if it is possible to combine many trees : peaches, apples, prunes, cherries, ginko, pears, apricots, peacans and a few bushes of blackberries/strawberries/blueberries(herbs) at the bottom. The only big no no I came across was walnut (black). My research is still early. But hey.
I knew there was a far north Pecan but it performs all the way up there? Wow that's amazing.
That being said, Pecan does produce Juglone in smaller quantities than Black Walnut. Might want to carefully buffer around it with something resistant to Juglone, Mulberry is hardy down to zone 4 and might be a good pick.
American Persimmon is borderline zone 4/5 so that might be another option for you.
[It's also possible the quantity of juglone provided by the Pecan is no big deal, that requires further research than I am willing to put in at this point.]
Not only is it possible to combine different trees in a food forest, it's highly encouraged. Large groups of like trees aren't forests, they're orchards or farms. One of the many advantages of food forests is that the incredibly diverse plant life slows the transmission of pest and disease between similar plants.
It was the peaches I was surprised to see on that list. I always think of them as a product of the deep south, forgetting how long people have been breeding them for different climates.
I'm in the middle of pecan's native range, grow much of my garden directly under a pecan tree and mulch with pecan leaves so in my experience that plant isn't horribly toxic to others.
Even if you have your heart set on black walnut, there are plants it plays nicely with. A fast search gives me an article from the Morton Arboretum that includes a list of plants sensitive to juglone and tolerant of them. The second list is much longer than the first. If you can plant enough tolerant plants between your walnuts and other plants, even they are possible.