When it is best to prune—or not prune
Plants in nature do not require pruning. We prune them to meet our needs, improve the size and sweetness of fruit, improve flowering of plants and have a good crop of fruit, every year.
We also prune plants for safety because we do not want trees or their branches to fall and cause damage or injury to people, and we prune for artistic purposes (topiaries and hedges).
We prune plants to make them fit into our landscape. That is not a good reason though, and it is better to pick plants that fit our landscape without pruning. This saves water and labor. The more we prune the plants, the more they grow and the more water they need.
The correct time to prune is, many times, based on your reason. Many gardeners start to think about pruning their trees and shrubs as soon as trees start turning color in fall and losing their leaves.
Most deciduous plants (plants that lose their leaves) are best to be pruned, in late January. This includes fruit trees, deciduous shade trees and most roses, with a few exceptions.
It will not hurt to prune fruit or shade trees as soon as the leaves have fallen off, but your trees will not start to heal the pruning cuts until the plant starts growing, next spring.
It is always time to prune dead, diseased, damaged (broken) branches off your plants. It is easier to identify these problems when the plants are growing, rather than after the leaves have fallen off. You should also remove suckers from the bottom of plants as soon as you notice them. So this should be accomplished as soon as you can, if you have not done so recently.
Spring blooming plants such as forsythia, lilac, Lady Banks roses or plants that flower only once, in spring or early summer, should not be pruned, in winter. It is best to wait until after they bloom. Pruning these plants in winter just reduces the flowers that would bloom in spring.
Flowering peach, flowering cherry and flowering crab apple should also be pruned immediately after they finish blooming, next spring. This allows you to have a spectacular flower show in the spring.
After the plant has finished blooming, it needs to be pruned. For most of these plants, that would have been late spring or early summer. If you prune them during the winter, you are just removing the future flower buds and decreasing the flower show for the coming spring.
The best time to prune evergreen trees and shrubs is during their growing season, which is mainly spring through fall. This allows the plants to heal quickly. Evergreen trees and shrubs do not lose their leaves in the winter. This includes pines, junipers, magnolias and other plants that have leaves on the plant yearround.
There are two types of evergreen plants: broad leaf evergreens and conifers. Broad leaf evergreens are typical landscape shrubs such as Indian hawthorn and privet. Conifers are cone-bearing plants such as pine trees, junipers and cypress.
Broad leaf evergreens can be pruned any time, but it’s best to do so after they flower. Conifers are best pruned during their growing season, which is fall and spring.
Herbaceous plants such as day lilies, fortnight lilies and ornamental grasses are best not to have the dead or damaged leaves removed until next spring. Even though the dead leaves look bad on the plants during the winter, they insulate the roots. Removing the dead leaves then could actually kill the plants, by allowing the roots to freeze.
Examples of herbaceous plants include agapanthus (Lily of the Nile), day lilies, fortnight lilies, yarrow, asparagus fern and Shasta daisies.
If your first impulse is to grab the pruning shears and attack your landscape shrubs, roses and fruit trees, stop! It is best not to prune any plants until the end of January. At best, you can clean, sharpen and adjust your pruning tools now, but it is not time to do much major pruning of your plants.