Some trees just do not have roots in all the places you really want them. There are a number of ways to get roots to grow where you need some. These first pics are of apprach grafting seedlings to add roots to a trident maple.
The seedlings were approach grafted at the end of last winter.
Time to see what has happened. First step, comb out the roots and wash them off a bit.
One of the seedlings at the back and the one at the side have not joined up with the trunk so I'm trying again. Remove bark on the trunk and on the seedling and put them together again, this time nailed on a bit more securely.
The other seedlings that appear to have joined ok are cut back to get the new roots to feed the tree and join up even better. you can see I've left stubs until I'm sure the roots are actually feeding the tree. The 2nd from the left joined up quickly and was cut back earlier so it is time to reduce the stub and start the scar healing over.