A common concern among gardeners is when to prune a tree. Pruning is essential for healthy trees, but timing is important for maximizing the benefits of pruning and minimizing negative effects.
For most deciduous trees, the best time to prune is late winter or early spring while the plants are still dormant. This allows you to clearly see the framework of the tree and make cuts that will have the least impact on overall growth. This is the ideal time for major thinning and to remove dead or diseased branches. It’s also the safest time to prune best time to prune a tree because the leaves have fallen, making it easier to identify limbs that could fall during a winter storm.
Evergreen conifers, such as spruce, pine and fir, are best pruned in late winter or early spring as well. These trees don’t grow throughout the year, so pruning before new spring growth directs vigor to desirable branch crotch angles and denser growth. They may be trimmed slightly throughout the growing season, but removing too many buds can lead to unsightly stubs and a lack of needles or foliage.
Some deciduous shrubs, such as lilacs and spring blooming perennials, can be pruned in the summertime after they finish flowering. However, light pruning in the summer (to control height or width and to get rid of stubs from last year’s growth) can stress the plant, leading to smaller flowers or less fruit the following year.
If you have a very large evergreen, such as a mature spruce or hemlock, consider a technique called “heading back” in the spring to reduce their size. This is accomplished by pinching the tips of new growth (“candles”) when they are about 2 inches long, using your fingers or a sharp knife rather than shears. Pinch one-half of each candle, and the remaining candles should grow more densely. This technique can be repeated in late summer to mid-summer for additional growth reduction.
The worst time to prune is the fall, particularly for oaks and elms. Open pruning wounds on these susceptible species are prone to infection by beetles carrying diseases such as oak and elm wilt. In addition, regrowth that results from fall pruning uses energy reserves that would be better spent preparing for winter dormancy.