The most widely accepted way to prune your juniper is to allow the foliage to grow — to provide energy and strength to the tree. Then, if the foliage extends beyond the desired silhouette of the tree, we trim off the overgrowth with a pair of sharp shears. Juniper trees can withstand aggressive pruning well but keep in mind that they cannot come from any bare tree parts. It is best to prune juniper bonsai in the early spring and summer during their active growing period. I hope my advice will help you, and I hope you have great results when trimming the plant!