Q.My Friend Has Five Mulberry Trees, Four Of Them Bear Every Year. The Fifth One Is Always Loaded With Fruit, But The Tree Drops The
m before ripening. The tree that drops the fruit is in the middle of her yard. The ones that bear are in the edge of the woods beside her drive.
Certified GKH Gardening Expert
This article will help figure out why the fruit drops. I suspect inadequate pollination, since it is further away from the other trees that bear fruit. Some types of mulberry trees need a male pollinator tree and that may be the case here. The pollinator tree may be in a neighbor's yard. Another possibility is because the tree is in the middle of the yard it is in a windy site, which will knock fruit off the tree.
https://www.gardeningknowhow.com/ornamental/trees/fruitless-mulberry/mulberry-fruit-drop.htm