Ash trees, of all the yellow, white, and black varieties, have been a staple across the United States for many years. Sadly, however, many ash trees have recently fallen prey to the emerald ash borer, an invasive species that likes to feed on ash trees' vascular tissue, killing the tree off within a few years. A tree needs to be really healthy and strong to fight off an ash borer infestation. There's nothing you can do to guarantee your tree will make it, but you can at least take a few precautions, especially when trimming your ash tree, to ensure you're not doing more harm than good and putting the tree's health in jeopardy.
1. Trim the tree before spring.
Most guidelines will tell you to trim your tree in the spring. However, trimming a tree in the spring requires some really careful timing, as if you trim just a day too late, you risk exposing the tree to insects like the emerald ash borer. It's better for your ash tree to trim while it is still winter outside. This gives it some more time to heal its wounds before the bugs become active. (They are sometimes attracted to the sap of fresh wounds.) It also ensures you don't remove any new, active, growing bud tissue from the tree. The tree will not waste energy developing new growth just for you to trim it away — this will improve its health, overall.
2. Don't remove branches without a reason.
Every wound you create increases the risk of emerald ash borers being attracted to the tree. So this is not the time to remove branches just to make the tree look better. Only remove a branch if it is dead or infected, rubbing against another branch, or in danger of hurting your home or another structure. The less you trim away, the better.
3. Leave branch stumps behind.
Your instinct may be to cut branches flush with the trunk for a tidy look, but it's actually better for the ash tree if you leave behind little stumps from every branch. This makes it easier for the tree to heal, so it will have more vitality left to fight off insects and infestation. It also reduces the amount that the wounds bleed, so insects are less likely to be attracted to the tree in the first place.
Taking some precautions when trimming an ash tree can help reduce your risk of an emerald ash borer infestation. These are really invasive bugs and your tree may ultimately still meet its demise, but at least you'll know you did not make things worse with poor trimming choices.
For more information about tree trimming, visit a website like http://www.prtree.com.