Q: I have a mugo pine in front of my house that is out of control. It is seven feet in diameter and encroaching onto the sidewalk in two directions. It needs to be cut back by half to get it under control and fit properly into our landscape scheme. How much can I cut back at one time?
A: Mugo pine is labeled and sold as a dwarf, densely-growing plant but, according to woody plant guru Michael Dirr, “One of the problems with this plant is that it doesn’t read the advertisements.” It is true that some mugo pines grow slowly to four feet in height and width. Others, after a dozen years may be twice that size.
Achieving the size you want may be difficult. If you shorten the limbs by half it is likely that no dormant buds will be left on the remaining stub. Therefore no new growth will result and the limb will die. If you are lucky, you can shorten the longest limbs back to existing interior limbs which have needles on them now. Those limbs should be left alone for this season.
Next year, assuming the pine is the size you like, clip off the tip of the “candle (green center growth) on each limb once it is an inch long. This will thicken the foliage and keep the pine small. If your proposed cuts will leave little foliage on the pine, prune it with a shovel and replace it with another small conifer.