Pine shrubs, like the mugo pine, are technically trees that can be shaped into a shrublike shape. Trimming, or pruning, a pine is an important part the tree-shrub's maintenance if you want to maintain a shrublike size and shape. Prune and trim pine shrubs in the summer when new growth is forming. Iowa State University recommends pruning pine shrubs between June and early July. A second light trim in the late summer will keep your pine shrub looking neat for the coming winter.
Look at the overall shape of the pine shrub and identify the areas you want to trim. You must keep pine shrubs small through annual pruning, beginning when the plant is a sapling. Left to themselves, pine shrubs will quickly become full-size trees.
Identify the new growth of candle-shaped greenery on the end of each branch. Using your fingers, pinch off half the new growth. This will force the new growth to remain close to the center of the shrub.
Cut off unwanted limbs close to the trunk of the shrub. Use a sharp, clean pruning saw for large branches; clip smaller branches with sturdy, sterile pruning shears.