I have heard that currants make a good companion to hackberry.
Here is something I found
The little-known “walnut/hackberry guild” (a term from Tim
Murphy, permaculture garden designer, as reported in Gaia’s Garden: a Guide to Home-Scale Permaculture, Second Edition, 2010) can recreate a natural-affinity plant group that can work in the garden for you, provided you have well-drained soil.
Here are juglone-tolerant shrubs and plants that you can set under/near your walnut: hackberry shrub, currants
(esp. with hackberries); the Russian Olive (a nitrogen-fixer) and its relative goumi (fruit); in
addition, wolfberry or goji berry (Lycium species), elderberries, hazelnut, crocus and daffodil. For more
info: www.missouri.edu/newsletters/meg/archives/v6n4/meg4.htm
I have a lot of hackberry where I live and have noticed that Tradescantia (spiderwort) grows very well even right next to a mature trunk. I would add mulberry as a companion to hackberry since they appear together all the time.
Celia Is the soil around your mother hackberry well drained? I ask because I have had pretty good luck growing things around hackberry and tree of heaven (another aleopath) and am wondering if it has to do with the drainage and slope of the land. I like your theory about the berries, and I think nature supports it to some extent when you look at wild strawberries under hackberry in the forests.
In my forest garden I have a 3 foot hackberry that I keep chopped back quite a bit, it is near strawberries, clover, cilantro, daffodils, basil, snowpeas, and asparagus. These things all seem to do ok so far.
Good luck on your desert food forest.