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A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Friday - July 13, 2012

From: Denton, TX
Region: Southwest
Topic: Diseases and Disorders, Watering, Trees
Title: Redbud leaves turning yellow in mid-summer
Answered by: Guy Thompson

QUESTION:

The leaves on our redbud trees are turning yellow. The yellow leaves are pale with no other spots and no dark veins. I don't know for sure which variety of redbud they are or how old they are (more than 10 years old). The heat and drought of 2011 hit us pretty hard. Is this a result of last year's drought, or is there something else going on? What can we do to save them? Thank you!

ANSWER:

Redbuds and many other trees normally drop some leaves early when drought-stressed.  This is an adaptation to reduce the need to take up moisture from the dry soil.  Don't worry too much if the branches are still alive (scrape off the bark on a defoliated twig to see if it has green and moist tissue) and if 50 % of the leaves remain green.  New leaves will appear next spring.

If a great number of leaves are turning yellow, the trees may still be drought-stressed.  Drought stress can show up even a year or two after a drought because part of the root system has not yet recovered.  If that is the case, you should make sure that the soil around the trees remains moist.  Deep watering throughout the root zone (out to the drip line) once a week will assure that the trees are not short of water.  Mulching the area under the trees will help conserve soil moisture.

Plant nurseries around the country sell several varieties of redbudCercis canadensis var. texensis (Texas redbud) is more drought-resistant than Cercis canadensis (Eastern redbud) and less drought-resistant than Cercis canadensis var. mexicana (Mexican redbud).  The seed pods of Texas redbud tend to be reddish in color while the Eastern redbud seed pods remain green.  That may help you identify yours.

Drought stress would make the trees more susceptible to disease.  It is possible that you trees are not drought-stressed but suffering from verticillium wilt.  Here is a web site on this subject. 

Good luck in keeping these attractive trees alive!

 

From the Image Gallery


Texas redbud
Cercis canadensis var. texensis

Eastern redbud
Cercis canadensis

Mexican redbud
Cercis canadensis var. mexicana

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