AgEBB-MU CAFNR Extension

Green Horizons

Volume 22, Number 3
Fall 2018

Urban Forestry

Tree Response to Drought

By Jon Skinner| Missouri Department of Conservation

We have received some rain in the last few weeks of August, but the damage to trees is already done. The drought is at severe to extreme categories in southwest Missouri, and extreme to exceptional in the northwest quarter of the Show-Me State. In these low moisture conditions, trees react in both the short and long term to this stress.

Short term responses can include:

• Wilting of leaves
• Scorching of leaf margins
• Dropping leaves early - brown, yellow, or green
• Early fall color
• Twig dieback, especially in the top of the tree
• Death of recently planted or already sick trees

Every species responds differently to drought. For example, red buckeye will drop leaves and be able to leaf out next spring. Hackberry and river birch regularly drop leaves during the summer months.

Besides dropping leaves, there are other physiological effects drought has on trees. But, they all add up to a weakened tree. The weakened tree is then setup for longer term effects, such as less growth the following year (or years), and greater susceptibility to attack from pests. These effects could last for several years and some trees succumb. We saw this during and after the 2012 drought with many older black oaks dying. They were attacked by various insect and fungi pests with Hypoxylon being the most visible. Keep these thoughts in mind as you care for your trees in the future. Long memories will help you understand your trees better.

Contact your local urban forester for more information on how to care for trees during drought.