Early fall color in deciduous trees may indicate trouble

Last Updated: 
September 30, 2008

CORVALLIS - If you see a maple, ash or other tree that is showing early fall color, pay attention. That tree may be in trouble, says Melodie Putnam, Oregon State University Extension plant pathologist.

"Normally most trees start to put on their autumnal colors later in the year, especially after a good brisk cold snap," explained Putnam, a diagnostician at the OSU Plant Clinic. "However, yellow, red or purple leaves at this time of year on trees that are not normally highly colored (such as purple plums) are a symptom of stress."

Look closely at the tree with off-color leaves. Does it have bare branches in the upper crown? Is there a wound on the stem from mechanical injury or sunscald? Is the tree in a zone where rooting is restricted? Was the tree never watered this summer?

"If the answer to one or more of these questions is yes, then it is no surprise the trees are starting to turn already," said Putnam. "Root disease, recent disruption to roots from construction or grade changes, compaction from vehicular or foot traffic and self-girdling roots can also result in premature fall colors."

Can anything be done? Yes, she says emphatically.

"Try to determine the source of the stress and correct it," Putnam said. "Little can be done about wounds that are already present, except to prevent further wounding."

Mulching around trees will remove the temptation to mow or weed right up to the trunk.

The most common cause for early fall color is insufficient watering during the summer, said Putnam.

"I often hear 'But it was so wet all winter,'" she said. "Yes, it was wet, but normal rainfall in the summer is thin, and during all of July and August there may not have been two inches total rainfall. Eight weeks with a full canopy of leaves and the sun bearing down, increasing evaporation, can be a long time without any supplemental water."

Make sure the tree receives sufficient water during the summer. And don't forget to mark or make note of this year's trees at risk (those showing fall colors early). These should get special care next year, including summer irrigation and spring fertilization.

Author: Carol Savonen
Source: Melodie Putnam