Browning trees may be dormant, not dead

Mother Nature has turned up the heat, and many landscape plants are paying the price. Leaves are curling, scorching or just turning brown and falling off. Although we’ve had rain, it may be too little, too late. If it looks like autumn has struck your yard, with crunchy leaves blowing around in the wind, be concerned. Take time to inspect trees to see if you need to take action.

Here are some problems to look for and what can be done to stop them: Normal leaves are green and full of chlorophyll, a chemical responsible for capturing energy from the sun and converting it into sugar and oxygen. In fall, green chlorophyll begins to break down so other pigments emerge. Recently, however, chlorophyll is being lost for a variety of reasons and not because fall is on the way.

The biggest cause for the change in color is the weather. During the past several months, there has been a variety of weather patterns. We have had an early warm-up followed by several late cold snaps, then 6 to 8 inches of rain in a two-week period, ending with high heat and humidity. Welcome to Kansas.

Although we can cope by going indoors and adjusting the temperature and humidity in our homes, landscape plants do not have that luxury. In many cases, trees that endure stress will shut down and go dormant. This means losing leaves, which gives the appearance of a dying tree. Use a fingernail or a sharp knife to scrape a little bit of bark off and inspect the underlying tissue. Healthy tissue that is just dormant will be green and moist. Dead tissue will be brown and dry.

Likewise, inspect the leaf buds. Healthy dormant buds will be plump and firm. Dead buds will be dry and papery. If stem tissue and leaf buds are dead, this is a bad sign. If the tissue and buds are alive, this may just mean the tree has gone dormant and will survive.

Above-ground leaf problems may be the result of below-ground root problems. Girdling roots, improper planting technique, poorly drained soils and root diseases tend to show up during the stressful time of the season. Roots that are not functioning properly cannot supply enough water to the leaves, which results in leaf-scorch.

Do a little digging to uncover the problem. Twine left tied around the base of the trunk needs to be removed. Girdled roots may be clipped, but this is difficult to do on a mature tree. Improper planting – such as planting the tree too deep – in the long-term may mean tree replacement.

Not only is the temperature rising, but so is the amount of insects. Pests such as whiteflies, aphids, spider mites and lacewings suck juice from the leaves, causing them to dry up and fall off. A close inspection of the underside of the leaves will reveal these tiny creatures as they feed. To control, use insecticidal soaps and other general-use insecticides according to the directions on the package.

But what about red leaves? It seems the maples, burning bush, rough-leaf dogwood and many other landscape plants are turning red. Again, it is a response to the weather. The red pigment, called anthocyanin, is produced as a response to stress.

This year could have been too wet, too hot early in the season and too cold at night. What does this mean long-term for the plants? It is a wait-and-see situation. It is doubtful that the plants will produce new leaves this late in the season. Therefore, they will have to live on stored energy until next spring. So for now, there is little you can do other than hope for the best.