With all this heat, many of the leaves on my dogwood tree are brown. Is it dying? TL

Your tree is likely not dying but suffering from something called environmental leaf scorch. Environmental leaf scorch happens when the plant cannot uptake enough water to meets its needs during harsh summer conditions, and we have been having plenty of that recently. Sometimes, even when we are providing supplemental watering, they still can’t keep up with the extreme heat.

With leaf scorch, the leaves start to turn brown at the edges first, because the edges are the furthest away from the primary veins of the leaf. When conditions are bad enough for an extended period of time, the entire leaf can dry out and turn brown. Then, the trees start to drop these dead leaves as a defense mechanism.

One thing that can contribute to leaf scorch is tree placement. For example, your dogwood is primarily an understory tree, meaning it prefers to be planted under other trees. If it’s planted in full sun, it is more vulnerable to leaf scorch. Trees on the west side of the house are also more susceptible due to their exposure to late afternoon sun. In addition, trees that are next to a home, driveway, or sidewalk have restricted root growth which contributes to the roots not being able to supply the water needs of the tree.

Even though the primary cause of leaf scorch is a lack of water, leaf scorch can also be caused by construction damage, over-watering, over-application of fertilizer, or a loss of roots due to a dry spring or winter.

Damaged roots due to construction is fairly obvious to understand, but over-watering can seem confusing. Soil is made up of about 50% solids, 25% water, and 25% air. Over-watering reduces the amount of air and actually inhibits the tree’s ability to uptake water. If you are concerned you are over-watering, there are inexpensive soil moisture gauges that will help you figure that out.

Too much fertilizer can burn the root system leaving it unable to pull up water. This type of damage can happen on only a portion of the tree or the entire tree depending on where the fertilizer was applied. As a general rule, if you are fertilizing your yard, your trees don’t need any additional fertilizer.

To prevent root damage in a dry winter or spring, give your trees a good soaking once a month during these months by watering in the root zone. In larger trees, these root zones can extend up to several times the height of the tree, so this entire area would need to be watered.

In spite of its unsightly appearance, in most cases, leaf scorch does not affect the viability of the tree since they have likely already stored up enough energy from the growing season and in a few weeks, they will be dropping their leaves anyway. 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