Gardeners ask me if it’s time to prune. Late summer and early fall pruning can encourage new growth, which will not have time to harden off before freezes occur. If freeze damage happens, the health of the plant can be adversely affected. This is particularly true for roses, which should not get pruned until April. Once trees have dropped their leaves and are dormant, usually in late October to November, pruning can take place. With leaves gone, you will be able to see which branches need to be removed, reshaped or reduced. Evergreens, such as pine and spruce, can be pruned after a hard freeze. This late pruning will reduce potential beetle or borer attack.
For some trees, late summer pruning is advised. These include maple, birch, beech, poplar, elm and willow. These trees have a tendency to “bleed” profusely if pruned in the spring.
However, as with any gardening, there are exceptions. Any dead, diseased or damaged wood should be removed as soon as possible, even on roses. With diseased plants, be sure to disinfect your tools with isopropyl alcohol so you don’t infect wood on the same plant or on other plants. I prefer isopropyl over a bleach/water mix because it doesn’t damage tools and is easy to carry in a spray bottle.
Only non-spring blooming shrubs should be pruned in the fall and winter. Rather than shearing a shrub, selectively thin branches to reduce the size or improve the shape. While shearing is a faster technique than selective pruning, it often leads to plant health problems. These include a tendency to spider mite and aphid infestations, browning due to water loss from drying winds and weak and unnatural growth. When pruning selectively, remove dead, dying, interfering or misdirected branches. This includes living branches that are blocking windows, walkways or are safety hazards. If you prune spring blooming shrubs, such as lilac, in the fall, you will remove the flower buds and you won’t have blooms next spring.
Keep tools sharp, clean and disinfected. I use long-handled loppers, a two-way saw and hand-held pruning shears. My saw cuts going forward as well as back, which I find easier to use. My hand-shears are bypass shears and prune with a sharp cut rather than squishing the end of stems as anvil shears do. If there are big limbs, high branches or limbs near power lines, hire a certified arborist to do the job correctly and safely.
JoAnne Skelly is associate professor and Extension educator, Emerita at University of Nevada Cooperative Extension. She can be reached at firstname.lastname@example.org.