News release: Trees and Drought, Part II

Tim Baker, MU Extension Horticulture Specialist
102 N. Main, Suite 1, Gallatin, MO 64640

Release date: March 7, 2013

Title: Trees and Drought, Part II

Last July, I wrote a column discussing the effects of the drought on trees. I was receiving a lot of calls from anxious homeowners wondering if their trees were dying.

My answer to them was perhaps, but probably not. Our trees were certainly showing major stress in the heat and drought.  But they weren’t necessarily dying. Dr. Chris Starbuck, our Extension State Woody Ornamental Specialist (now retired), told me that he had even seen trees completely defoliated by drought recover when given water.

So my answer to these homeowners was basically to irrigate if possible, and wait and see what happened with the 2013 spring season.  Even if a tree had completely defoliated, give it a chance, and see what happened when everything started leafing out.

We are already seeing warmer temperatures, so spring can’t be far off. It will soon be time to carefully observe any trees in question, and compare them with nearby trees of the same species.

For deciduous trees, if everyone else’s oak trees leaf out, for example, and your oak tree does not, then your tree most likely won’t recover.  Just give it a chance to see what happens.

Evergreens present a different problem. If they are totally brown this winter, there is a strong likelihood that they have died.  Some species, such as yews, can recover if there is any hint of life left in them, so I would give evergreens a chance too.

I have seen people already taking down totally brown evergreens this winter. Most likely, the tree has died. This is especially true with species such as pines.

But even pine trees can surprise you sometimes. When I lived in the Bootheel, we owned a house that had two pine trees in the back yard, of the same species.  One of them started looking bad, and then died.  Since it didn’t come back, I cut it down. A few years later, the other tree started looking pretty rough, although it never turned completely brown.  I thought that it was on the way out too.  But it came back!  I was amazed.  That’s why I say it’s always a good idea to give your tree a chance.

The other complicating factor with evergreens is that they are not dormant in winter, compared to their deciduous neighbors. Evergreen leaves are still calling for water from their root system, to transpire that water out through the leaves, all winter long. The problem is when the ground freezes, the roots can’t take up water, and the leaves suffer.

So if your evergreen tree is looking somewhat marginal, it could just be because it can’t take up water when the ground is frozen, and that water is in short supply anyway, due to the drought. This is another reason to wait for the spring thaw, and give it a chance.

By the way, if you have a particularly valuable evergreen tree, you can spray antitranspirants that slow down the transpiration process in the winter.  I wouldn’t use it now, but consider it for next winter.  What I would do now is make sure your tree has plenty of water. You’ll need to irrigate soon, assuming that the drought continues.