Janet,

I notice you don't have any pictures, but posted this in the gallery section; are we missing the photos that tell more about your post?

Anyway, pruning roots is not a way to get them to grow. They will hopefully try to RE-grow, but won't grow more than they would have anyway. Like building a dam to supply energy to drive pumps that would pump water down the waterway, pruning is not needed for roots to grow. Root pruning may need to be done for pot-bound roots, but I'm not sure if that's what you had in mind.

Thank you for your reply. I'm new around here, so probably posted this in the wrong section. I'm not necessarily trying to get them to grow more, but to fill out, like they would in a pot. Or perhaps I should say, I'd like to trim the roots so I can get them in a smaller pot. Perhaps I can just dig them up this fall and put them in pots, trimming the roots if necessary. Thanks again!