The black maple in my front yard has been beautiful for the past week, but I’m afraid the precipitation and wind over the next couple of days will put most of its fire orange leaves on the ground. The ash trees in the back yard are likely to follow suit, especially if we get a hard freeze. The oaks are just beginning to color up, though, so there’s still some fall beauty to look forward to.
People may stop looking at their trees as the beautiful leaves blow away, but leaf drop is a signal that it’s prime time for tree maintenance. Trees may be entering a period of dormancy, but their roots will continue to grow until the soil freezes. Young trees, in particular, may need extra moisture going into the winter, even though we’re getting a little rain as this is written. Young, thin, tender bark is vulnerable to splitting during prolonged cold dry winter conditions. Conifers, with their evergreen needles, continue to lose water all winter and may suffer if they go into winter without adequate moisture. It’s best for trees to enter the winter in a well-hydrated condition. Several slow, deep waterings before the soil freezes in early December will be desirable if we don’t get more fall rains. It’s a small investment to help your trees come through the winter in good condition. They’ll repay your investment in a little care now with a lifetime of beauty.
It’s also a good time for maintenance pruning of most shade trees. Young trees often need "training" if they’re to grow tall and straight. I planted a bur oak in my yard a couple of years ago and it’s developed a side branch near the top that is way too long. It has become the main lead in what ought to be a straight trunk. A shorter, but straighter, branch should be the main lead, but too much energy is going into the wayward branch. I could just cut off that branch, but the little oak needs as much leaf surface as possible next year to gather sunlight. Instead, I’ll just prune off the outer end enough to allow the desired straighter branch to become the future trunk. Virtually all of the existing side branches on this young oak will eventually be pruned off as the tree grows taller. Some side branches, as yet unformed, will eventually become the main first branches of the tree. Work done now will help to insure that the young tree matures with good shape and strong branch structure.
Other things to look for include weak forks, where the angle between two branches is too narrow. Bark is often trapped in the fork as the two side-by-side branches grow larger. This leads to a weak connection that is likely to break during some future wind or ice storm. Breaks like this often tear a lot of bark and leave a big wound that is slow to heal. Broken weak forks can even wreck the whole crown of a tree if not caught and corrected soon enough. Branches that grow inward within a tree’s crown or crossed branches may lead to future problems, too. They can interfere with the growth of other branches or lead to worn bark when two branches constantly rub each other. Injured bark is a likely access point for disease and insects.
Give your mature trees a good looking over, too. Leaf drop exposes the branches so that you can see if the past year’s storms have caused any damage. It’s best to prune damaged branches back to the nearest main fork or even the trunk. Pruning in the fall allows the resulting open wound to dry out so that it’s a less attractive entry point for insects or fungal diseases next spring. Trees naturally create a hardened barrier in the wood directly under an injury that is more resistant to insects and disease. Trees repair wounds by covering them with new wood called callous tissue. The more rapidly this forms to cover the wound, the better. Wound dressing paint is no longer recommended to cover pruning cuts since it can interfere with a tree’s normal healing process.
You can do much of the necessary work yourself on younger trees with only a small investment in some simple tools. You may need the help of a qualified tree service to do higher work, though. They’re trained and equipped to do that kind of work safely. It’ll cost you something, but the investment in your trees is worth it. Your trees will pay you back many times over.
(Steve Lekwa is a former director of Story County Conservation.)