Question
Dear Jim,
  What is the best time of year to trim these. My sister-in-law has three that were shaped into balls and spirals when she bought them, but hasn't trimmed them in two years and wants me to try to reshape them. Should I wait until later in the fall when the hot days are over, but before frost?  How aggressively can they be trimmed?  Can I trim to their original shape at once or should I do it slowly over a couple of seasons?
 Jane

Answer
The best time of the year to prune evergreens is in the spring while the weather is still cooler. This allows the plant to produce new growth that will cover the pruning marks for the rest of the season. To keep a plant at a certain size you have to prune it every year.

Prune 2-4 inches at a time or back where there is still green leaves. beyond this point the branches may not put on new leaves. It may take a couple of years to reach the pint that you want. But since it has only gown two years you should be able to shape them the first year BUT the tree will be larger than the "ball" shape two years ago. It maybe hard to get it too the same size as two years ago.