March through mid-April is an excellent time to prune shade, ornamental and fruit trees. Pick a nice day in the 40 degree to 60 degree range with low winds and you will have very pleasant working conditions. Our crews started field pruning this week, taking advantage of a stretch of wonderful March weather.
This is the time of year when it is unlikely that viruses, bacteria, insects and fungus will infect fresh pruning cuts, since these pests are largely dormant until late April. Use a sharp hand saw, and a freshly sharpened hand pruner to make cleaner and easier cuts.
Some trees like maples will bleed sap when pruned during the next 30-40 days, but research has shown this does not hurt the tree, and will stop in early to mid-April. The goal of pruning is to create a strong, lasting and good looking structure in each tree. Pruning before the trees leaf out makes it a whole lot easier to judge the structure since no leaves are present to obscure your view.
PRUNE EARLY AND OFTEN. This does not mean every day or even monthly. It means that during the first ten years after you plant a tree, you should prune it every year, or every other year to gradually establish the best possible structure that can withstand heavy wet snow, ice storms, and violent thunderstorm winds. By pruning often, you remove weak or problematic branches when they are small diameter, and the pruning wounds are small and heal over very quickly, minimizing the chance for rot to get going inside the tree.
Most deciduous trees have better structure when they have fewer and stronger branches. Prune out branches that leave the trunk at very steep angles of 60 degrees to almost straight up (90 degrees). Branches that form the strongest attachments to the trunk leave the trunk at lower angles from 45 degrees down to 0 degrees (horizontal).
Avoid cutting off a branch exactly flush with the trunk. Cut close enough to avoid leaving a stub, but leave intact the branch collar, which is the slight widening of the branch where it meets the trunk. This will sometimes leave the appearance of low bumps along the trunk, but assures smaller wounds that heal over quickly, and in one or two growing seasons the bumps will disappear as the trunk grows thicker. If you leave a stub of a 1/2 inch or more, healing will take several years longer. Same for cutting flush with the trunk, where the larger resulting wound will take years longer to heal.
Try to remove only about 20% to 25% of the canopy at any one pruning. If a really steeply attached branch needs to be removed to avoid future splitting during a storm, do it right away, even if this leaves a large gap or unbalanced area in the tree canopy. If you wait, the wounds and gaps only get bigger. The sooner you create the gap, the sooner small new strongly attached branches can grow into the area due to available space and sunlight.
On young trees a really good structural pruning of a bare leaved tree often leaves a tree looking a bit like a stickman, and causes a lot of consternation for people who think the tree has been ruined. Most trees that have been artfully pruned into an awkward looking silhouette in March will look fabulous by mid-June, turning the person who pruned the tree from a neighborhood villain into the local wiseman.
Good luck with your pruning and have a wonderful spring. It’s just around the corner!