I am growing trees in ground to use for future bonsai. I am planning on them being in ground for 5 years or more. If i want to cut the surface roots with a shovel to start getting more root growth closer to the trunk, what would be the time of year to do it? I am mainly thinking about D trees. Maples, hornbeam, Elms. Also, at what point would you start thinking about doing it, every year, or every other year, after they are established? Would it be different for azaleas, or any type of flowering, or fruiting tree?