Q. When and how do I prune mature junipers?
Because they lack the dormant buds that broad-leaved evergreens such as hollies have in abundance, narrow-leaved evergreens such as junipers can’t be pruned heavily. They produce new growth in spring and fall, so it's best to prune them in late winter or early spring, before new buds have broken. You may also do a little touch-up pruning in the summer months.
In general, most narrow-leaved evergreen trees and shrubs need little pruning. They should be pruned in a way that will maintain their natural form. To retain this shape, prune individual stems rather than shearing the plant. Always make your pruning cut to an upward-growing side branch--this type of pruning is called a "thinning cut." It afford improved light penetration but doesn't stimulate heavy branching. In contrast, shearing or heading cuts not only ruin the natural shape but also prevent sufficient light penetration, resulting in excessive foliage drop, disease potential, and dead zones in the center of the plant.
Rules for pruning narrow-leaved evergreens are quite different those for pruning other evergreens such as hollies. Many broad-leaved evergreens can tolerate severe renewal pruning. It’s hard to kill plants such as privet or hollies by cutting them to the ground--they simply sprout back from the dormant buds. Junipers and other narrow-leaved evergreens will not come back after this type of pruning. If you must prune narrow-leaved evergreens, you should start when they are small--usually the second year after they are planted. Pruning a little each year can keep the plants healthy and in their alloted space for many more years than would be the case if they were left unpruned. That being said, you can save yourself a lot of work and expense by spending a little time researching the mature size of the plant you have in mind to plant in your garden.
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service