If you find yourself gazing out the window in winter wishing the hustle and bustle of yardwork could be spread more evenly across the year, don’t despair. There is something you can do right now: prune your yard trees.
As a first order of business, you might consider whether your trees need to be pruned at all, and this is mostly a matter of taste. Just like your hair, trees will grow in ways you’ll appreciate when given regular maintenance. Removing dead limbs and selectively removing live limbs will create a more desirable shape and concentrate growth on the stems you choose to leave, molding young trees into shape or helping older, sometimes neglected trees regain good form.
What is good form, you might ask? Well, it depends on the type of tree. Good form in an apple tree encourages a central leader (the leading upward-growing stem of the tree), fosters light and air flow (to discourage fungal growth), and develops the lateral fruit-bearing limbs. Penetration of light and air, which can be achieved by removing crowded or touching limbs, allows for greater fruit production and easier access for picking and spraying. A central leader also makes for a stronger, simpler tree with more open spaces and sturdier limbs.
Pruning a non-fruit-bearing tree, such as a conifer, depends more on the pruner’s taste. Most homeowners growing spruces and firs attempt to emulate the classical form, a Christmas-tree shape, which can be achieved by encouraging one central leader and removing side limbs that compromise that form. If you have closely planted conifers, such as hemlocks, that you’re trying to grow in a screen-like fashion, you might consider encouraging several leaders and allowing a looser form.
However, many hardwood trees, such as oaks, have evolved their own special forms over time, and they may not thrive if you prune them into unnatural shapes. Also unlike conifers, hardwoods require pruning during specific times of the year – late winter is best for most hardwoods, but oaks should be pruned before April to avoid oak wilt – and pruning some hardwoods in late spring or early summer, like maples, butternuts, walnuts, and birches, will prevent excessive “bleeding” of sap.
Regardless of the type of tree you’re pruning, the techniques are exactly the same. First, each branch to be removed should be carefully vetted, because every cut into the trunk opens up a wound that can be invaded by tree-killing fungi. Trees have natural defenses against such fungi, but there’s no point in testing them unnecessarily. It’s safest to remove dead limbs first and go from there, never removing the branches that support more than a quarter of the foliage in any one year.
The technique for removing dead and live limbs is the same, though it is especially important to be careful when removing live limbs. With a small, sharp pruning saw, available at most hardware stores, you should cut just outside what is known as the branch collar, the bark that extends from the tree’s trunk which, when left on, becomes the circular mound surrounding the cut you see on well-pruned trees. It is important when pruning large branches to first cut most of the branch off at an outer, less-critical point, so that when you’re making your final branch-collar cut, the weight of the branch doesn’t tear the branch bark down into the trunk bark (think of pulling a hangnail too far). Make your cut from the top down, assessing your work along the way.
Determining how much of the tree to prune depends on a variety of factors, such as the tree’s age and the number of years since it was last pruned. Removing fewer, smaller limbs creates less stress for a tree than removing one large limb, and younger trees can close over pruning wounds better than older trees. Some trees require a thorough cleaning, including removing dead, diseased, crowded, and weak limbs, while others need only be thinned to help achieve a desired shape and to promote air and light penetration. Other objectives, such as raising or lowering the tree’s height for aesthetic or practical purposes, should be pursued with consideration of the tree’s health in mind.
If you undertake this important tree-care exercise in mid to late winter, you’ll maximize your tree’s chances of recovering and flourishing. It’s easier to see what needs to be done on a leafless tree. Also, many tree diseases are spread by spores, which are least active in the winter, and rapid spring growth will soon begin to close over the cut branch. Of course, dead limbs may be pruned any time of year, and even trees with live limbs that require immediate action (i.e., limbs that have been partially broken off in storms) are better off if immediately pruned, regardless of the season.