Do you have any upper portions left or did you chop it down to roots? When I have rampantly growing trees and shrubs, I prune or cut them, strip them of leaves, and store them leaning on the fence near the garden, and when I need sticks/poles/stakes for plant support I use these. Sometimes in the fall, I find that these branches have rooted during the growing season. Mulberry is one of those that sometimes root.
I've learned to use the ones that root too easily upside down from the way they were growing to prevent them.
Another way you could probably get them to grow roots is to ground-layer them.
I know some plants can be root propagated, but I'm not familiar with the technique.
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