I hope to grow Oak trees as Bonsai and wondering when when is the best time of year to prune their roots. I have a few growing and wish to vary their heights from 9 inch up to 36 inch

You are too late this year to re pot. You have to do it in the early spring. You can still be pruning to vary the height, but not the roots but the twigs and branches. However the first thing you need to grow is trunks then branches. Best place for them is in thee ground to get thickening of the trunks as quickly as possible

Thanks. Is it early or late spring or when the trees start to show signs of growth?

Ozzywelshborn wrote: Thanks. Is it early or late spring or when the trees start to show signs of growth?

m5eaygeoff wrote: You have to do it in the early spring.