By Andy Sherrod, Orchard Manager
I got a call recently from a guy with two big pecan trees in his yard. He said they weren’t looking healthy and he asked, “How do I treat them?” After a lengthy conversation about the history of the trees and the symptoms he was seeing, I concluded that his issue was water, or lack thereof.
The hot month of August is a good time to revisit the subject of adequate water. Here are some things to remember:
1. Mature pecan trees use a lot of water during July and August, about 150 gallons every day, to be specific.
That’s because the kernels are starting to fill with water. In fact, this stage of nut development is called “the water stage.” Water is being pumped into each nut, which will then be converted to nutritious pecan kernels during September. Without adequate water, the nuts are either aborted or poorly filled. If water is scarce, the trees conserve the available soil moisture for their future survival instead of devoting that moisture to creating lots of plump, healthy pecans now.
2. Most of the absorptive roots of a pecan tree are in the top two feet of soil.
Many people know that pecan trees have a deep tap root and falsely assume that the tap root can pull enough deep water from the soil to meet its needs. Not so. Water moves up into the tree through cells called phloem, which is located in the cambium layer just beneath the rough bark. Think of them as tiny straws. Longer straws must fight the effect of gravity so water moving up through the tap root has a harder time reaching the foliage. Consider this, it’s much easier for you to drink a glass of water through a straw twelve inches long than it is to drink from a straw twenty feet long. For trees to remain healthy they need lots of water in the top two feet of soil.
3. The grass under a pecan tree gets first call on water.
A pecan tree growing in a landscape with a healthy lawn must be content with the leftovers. Landscape sprinkler systems are designed to meet the needs of the grass, so one must “over water” the lawn in order to get significant amounts of water past the fibrous root system of the grass down to the root system of the pecan tree. Water is necessary for the development of quality pecans, but inadequate water can significantly stress a tree during these hot, dry summer months. It’s very likely that the man I recently spoke with on the phone was watering the grass on his lawn adequately, but his thirsty pecan trees were suffering.