Gardening: Too much water is causing a variety of tree problems

Q. Many gardeners are having tree problems. Here are some of the questions they have sent recently: My tree’s leaves are turning yellow; what is causing the color change? My tree has started dropping leaves; what should I do? The tree in my front yard has leaves that have started to curl, what is causing this? I have a tree showing fall leaf color; what is the problem?

A. This year, the amount of rainfall was 13.14 inches for the month of June or three times the norm of 4.28 inches. The last time we experienced this amount of rain was 1946. Most plants do not grow well when the roots are saturated and do not receive oxygen. These plants do not suffer as much from being deprived of oxygen as they do from the sugar in the roots. When the sugar converts into alcohol from lack of oxygen, the plant actually suffers from alcoholic poisoning.

Trees that can stand this wet, saturated condition are called mesic. During the flood of 1993, the 20-foot-tall bald cypress trees (Taxodium distichum) at the St. Louis Arch were completely covered by the flood waters, but none of them died. All plants that can live in flooded conditions for more than 10 days are termed mesic. Land that floods for more than 10 days straight per year are termed wetlands.

First, you need to study the location of tree and the surrounding topography. Does the tree grow in a slight depression in comparison to surrounding land? Does it grow at the the bottom of a hill? Does the soil contain a lot of clay, which holds water? Any of those conditions may be the main culprit of your tree’s problems.

Wet conditions put stress on your trees. The trees try to survive by dropping some leaves or they may change to fall color and eventually these leaves will fall off. Also, some insects notice that the leaves are full of sugar water and begin feeding on the undersides, causing leaves to curl.

As a general rule, trees survive flooded conditions better in a dormant state than a growing state. The healthier the tree is when it goes into a flood, the better its chances of survival. Warm, stagnant water is more harmful to the tree than cold, flowing water. Using a pump to remove stagnant water will help the tree.

You also want to consider the stability of the tree after flooded conditions subside. If there are too many dead roots below the surface, the crown of the tree will begin to die back. The greater the crown dieback, the higher the chances the tree is becoming a hazard. Check the surrounding areas to see what damages could be done if the tree were to fall over. Also, check large branches that could fall and cause damage.

It’s a good idea to check with an arborist to see what pruning may be necessary to prevent damage and what could be done to the soil to change the drainage pattern.

Trees that can stand the wet or mesic conditions include river birch (Betula nigra), pin oak (Quercus palustris) and tupelo (sour gum — Nyssa sylvatica).

This story was originally published July 9, 2015 at 5:04 AM with the headline "Gardening: Too much water is causing a variety of tree problems."