This is the time of year when our plants start to look a little rough. The relentless heat keeps pounding them every day. There appears to be some good weather news on its way to us, but that won’t negate the damage already done to our plants.

As you drive around town, you are probably noticing some of the leaves on trees starting to turn brown. That’s not an early warning of an approaching fall but instead is a survival strategy on the part of the tree.

Browning leaves, this time of year is likely the result of something we call environmental leaf scorch. As the heat keeps pounding down, it gets more challenging for the trees to uptake enough water to keep all the leaves thriving and green.

You’ll likely notice leaf scorch beginning to reveal itself at the edges of the leaves since the edges are the part of the leaf most distant from the veins of the leaves. As the heat continues and as water resources get scarcer, this browning of the leaves will continue until it affects the entire leaf. On some trees, this is the point it will start to drop those brown leaves. Others may continue to cling to the tree until the rest are ready to drop in the fall. This is really a survival strategy for the tree in that it is conserving water as best it can to survive.

Contributing factors may also come into play. For example, it’s not unusual for us to see dogwoods starting to drop some leaves now. Dogwoods are primarily an understory tree, meaning that it does best in the shade of other trees. However, it’s not that unusual to see a dogwood planted in full sun. If it is planted in full sun, you will almost certainly see it dropping some leaves now, if you haven’t already.

Trees planted on the west side of your home can also be affected more by leaf scorch since they are not shaded by the house etc. This would also be true of trees planted adjacent to driveways or sidewalks since they are not only getting the direct sun but also the reflected sun that bounces off of those hard, reflective surfaces. The trees we see in parking lots are a good example of trees that get bombarded with heat from every direction. Because of this, a lot of them aren’t looking that great right now.

Another factor that may be in play is that your tree may have suffered some root damage during the winter. This root damage may not result from physical damage but instead be due to a lack of water in the winter. Lack of water during the winter can damage roots which is why it’s a good idea to give your trees a good soaking about once a month in the winter if nature is not doing its part to keep our trees hydrated.

For the most part, leaf scorch and the accompanying pre-mature leaf drop are not cause for concern. At this point in the year, most trees have stored up enough energy to get them through the winter and leaves are going to begin dropping naturally in a few weeks anyway.

So, to help minimize this reaction to the heat, make sure your trees (and other plants) are getting enough water. And if you are out working in the yard, this goes for you too.

There is an exception to the “no worries” approach to pre-mature browning of leaves and that is when this browning is caused by bacterial leaf scorch. Bacterial leaf scorch is spread by insects who carry the disease as they move from tree to tree. With bacterial leaf scorch, you will likely notice it beginning in one particular area of the tree while environmental leaf scorch affects most of the tree, or at least the areas that get direct sun. Environmental leaf scorch also begins on the leaves furthest out on the tree. This is because it’s hardest to push the water out to those leaves furthest away.

Unfortunately, there are no effective treatments for bacterial leaf scorch. To properly diagnose bacterial leaf scorch, you would need to contact an arborist or bring a sample into our office so we can send it to the lab. The cure in the case of bacterial leaf scorch is typically the removal of the tree to keep the disease from spreading to other trees.

Fortunately, this time of year, it’s typically environmental and not bacterial. Good luck!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: Tom Ingram