Ask a Gardener – Ash Tree

Tuesday July 7, 2015

I live in Highlands Ranch and have a large green ash tree that only has leaves budding out on 2 side branches; nothing from the middle. I am worried it might be a victim of the ash bore beetle. Is my concern justified or is it just too early in the season to tell?

– Pat


It can be difficult to make diagnoses sight unseen, but we would say it is probably not an ash borer. As of right now, the Emerald Ash Borer (EAB) seems to be contained in a small area in Boulder. It’s also a little early in the season for borers in general. This time of year, adult Emerald Ash Borers and adult Lilac borers should only just be starting to emerge, so any real damage probably wouldn’t be noticeable for several more weeks. But we understand your concern. Borers, especially EAB, are extremely nasty pests, so it’s great that you’re keeping an eye out. Check out the Emerald Ash Borer page on our website for more info on detecting signs of EAB.


Insects generally attack weak or stressed trees first, so continue to keep your tree well watered and prune out any dead or broken branches. Systemic insecticides have also been shown to help prevent Emerald Ash Borer. The best systemic available to the homeowner is Bayer’s Tree and Shrub. You just mix the concentrate and pour it around the base of the tree for up to 12 months of protection.


It’s possible your tree is slow to leaf out this spring due to winterkill. A lot of trees are off to a slow start because of those early fall and early spring freezes that we had. They froze the sap that was still flowing through trees, so often you’ll see trees only leafing out from one side or from the bottom. To help the tree along, you can spray it with liquid kelp. Kelp contains phytoplankton, which help heal cell walls and encourage new growth. It’s a way to help the tree along without stressing it out with too much nitrogen fertilizer.