Southern California, zone 9. I moved into this house 1.5 years ago and theres 2 apple trees in the back yard. The smaller one leafed out last spring, produced small apples but a heat wave came through and burned everything up. I’m not sure what type it is and if it’s meant for zone 9.This spring, I have 1 branch from the whole tree with leaves and all sorts of root growth.
I would remove all those root sprouts and all the tree but the good branch. Its a pear, not an apple in the picture BTW. It might have gotten some disease or other issue on the rest of the tree. The growth at the bottom is the rootstock, it looks like pyrus betufolia from the shape of the leaves. From the amount of growth it looks like the tree not growing had some disease issue on the upper part, the roots are showing they are healthy with all that growth.
I don’t know what not enough chill could do but hopefully someone from your area like @Richard can comment on that.