I bought a couple of Buxus, to plant in stone planters either side of my front door. As the planters are built into the patio, I thought they would be bottomless ( so direct access to soil under) but it turns out they are stone bottomed with just one drain hole. Knickers Will Buxus live in a wide shallow planter like this? Depth is about six inches, but they are quite large in width. I don't need them to grow very large, as I want to prune them into balls to sit quite low under the windows. Any ideas? Thanks!