Trees Going Dormant Due to Extreme Drought

The gentle falling of leaves from trees is almost always associated with autumn and cooler weather.  One would expect to have to rake up leaves in the yard around late October and November. But how about seeing this scene in your yard in late August and when the outside temperature is 100 °F or more?  Much is the case in central Alabama due to the extreme prolonged drought.  Many trees all across the landscape are suffering from the heat and sure lack of water.  In response, a few trees have died but many species are beginning to call it quits for the year and are now shedding their leaves and going dormant for survival. 

When there is not enough water available, trees will first close the stomata or pores located on the underside of its leaves.  By doing so, it conserves moisture rather than releasing water vapor, which it does regularly during normal growing processes.  A tree may even develop additional feeder roots.

Extreme drought conditions can led to more dramatic responses by a tree including leaf drop. With little to no water, trees have no choice but to do what is necessary to survive.  By shedding its leaves, even in late August, a tree will dramatically reduce its need for water.  This helps keep their buds and roots from completely drying out. Generally, trees that drop their leaves will regain leaves after a rain or in most cases next year. When all of the leaves on a tree turn brown and stay on the tree during the middle of the growing season, the tree is all likely dead.

Different trees react differently than others when it comes to drought. Of course, site conditions and moisture content is always a factor on where a trees species naturally grows and how a specific tree will respond to drought. River birch, sycamore, and yellow-poplar, for example, typically loose their leaves. Oaks and hickories typically try to tough it out but in the long run may end up dying.  Dogwoods, which have shallow roots, suffer the most from heat and drought.  Dogwood leaves may turn brown along the edges, turn completely brown, or the tree may die outright.  Pine trees under drought stress may live through it but are much more vulnerable to being attacked and killed by pine beetles. All species, including oaks, may shed their leaves in extreme cases as observed this year.

The downside of a drought is the long-lasting effects.  Droughts are very stressful and can have a major impact on the future life of a tree.  A tree might not die this year but if additional stresses have occurred in the past or take place, including root disturbance, storm damage, soil compaction, or another drought, they could abruptly die at any moment.  Most trees that do die are a result of a build-up of years of problems and stresses and not just one particular thing.    

No one likes to see trees suffering from drought.  Brown leaves on trees just do not have that nice and attractive ornamental appeal, especially in the heat of late summer.  Maybe in November when one might see other leaves falling and covering the ground.  But if falling brown leaves means a tree is a fighter and going to be alive despite the drought, then let them drop.  Go get the rake and celebrate.  

For more information, contact the Tallapoosa County Extension Office at 256-825-1050 or the Master Gardener Helpline at 1-877-ALA-GROW.  You may also visit us online at www.aces.edu/Tallapoosa.