Leaf Drop on Trees

Home Grown  by Keith Reed
In the last few days, the Payne County Extension office has been receiving an unusually high number of reports of trees suddenly dropping their leaves. This happens from time to time; but for trees to do so in May when the leaves are full and green is very unusual. While we are not certain what exactly is going on, all signs point to weather related issues.

When we are trying to get to the bottom of an issue like this, the answer is sometimes found through the process of elimination after gathering as many facts as we can. In this particular issue, we know:
  • A variety of deciduous trees species are being affected.
  • The leaves, while not all perfect, are not showing much in the way of obvious disease or damage.
  • The problem is not isolated with calls coming in from Stillwater, Cushing, and Perkins.
  • The affected trees are growing on a wide variety of sites with differences in soil and microclimate.
When you add these factors up, the possibility of this being an insect or disease is diminished. Fortunately, we have very few pests that come through and indiscriminately cause this type of damage. Most pests (both insects and disease) have species they favor. In other words, if only oak trees were being affected, a pest attack would more likely be the problem.

Drought is the most common cause for causing this issue. We are pleased to report that is not the cause this time so we can thankfully take that off the list!

That leaves us with weather as the most likely cause. While it may seem like it’s been ideal weather for plant growth, that’s only partially true. While we have had adequate moisture and relatively mild temperatures, we’ve also had some bumps along the way. Probably most applicable to this situation would be the very early green-up, early warm weather with a couple of very significant cool-offs, less sunshine than usual, and several storm systems that have produced some isolated high winds and a bit of small hail.

The take home message is don’t panic! Trees that are otherwise healthy have the ability to put on additional leaves when the conditions are right for it to do so. Avoid the temptation to spray just in case. Unless you are targeting a specific problem, spraying is unlikely to help. As a matter of fact, it can often cause more harm than good.

The only additional care you might need to give trees that have been affected by this might come later this summer. If it does turn out to be a hot and dry summer, it would be helpful to give these trees enough water to help them avoid the stress of another premature leaf drop-from drought.

For more information of this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at keith.reed@okstate.edu, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

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