Whit, I hesitate to be the one to say this, but I suppose somebody's got to - its not the question of underplanting that's the problem, its the Flagpole Cherry in a pot. Prunus amanagowa, like other flowering cherries, spreads out surface roots as well as a few going down. The surface roots may reach at least ten feet away from the trunk of the tree, and obviously, its not possible for this to happen in a pot. Best in the ground frankly.

I agree with bamboo unless you're going to drastically root prune. If it is in the ground you can grow anything, even using it to support clematis.

well ,i have two in 18"diameter pots been there for close on 3 years,early spring i remove the top 2"of soil and renew it, and they are doing fine,the cherry s are not so tasty i leave them for the birds thanks for replies

Perhaps the tree you have is not Prunus amonogowa, the Flagpole Cherry - that rarely produces 'fruit' and if it does, it barely noticeable. You may have a dwarf fruiting cherry of some variety instead, which will be on dwarf rootstock?

thanks bamboo ,that sounds just like what i have, it is definitely grafted on to another "tree "

In that case, you could try popping a bit of trailing lobelia or something around the base, but I wouldn't use anything permanent.

thanks i shall do that