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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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Tuesday - September 12, 2006

From: Pasadena, MD
Region: Mid-Atlantic
Topic: Diseases and Disorders, Trees
Title: Yellowing of Thuja occidentalis leaves in early Fall in Maryland
Answered by: Joe Marcus

QUESTION:

Mr. Smarty Plants, I am from Maryland. Please help. I have planted 23 Thuja occidentalis Smaragd in my front yard a few months ago. Height of about 3 feet. Most of the trees have turned golden brown. Are they dead? or is that normal. What did I do wrong? They are suppose to be evergreens. Thanks Bonita

ANSWER:

Thuja occidentalis or arborvitae is an evergreen species. While it is normal of arborvitae - especially certain cultivars - to turn reddish-yellow during winter months, it is not normal for that to happen this time of year.

Some possible causes for your plants' condition are water stress (too much or too little), root disease which is usually related to watering issues, transplant shock, leaf miners or mites. From your description of your plants we would say that leaf miners and mites are not the likely culprits, but we can't rule them out. More likely, there is some issue involved in the transplanting and acclimation process that caused you plants to turn brown.

You should talk to your local nurseryman, arborist or cooperative extension service about the problem as someone may need to actually see your plants to give you a proper diagnosis. You are fortunate in the state of Maryland to have an excellent cooperative extension service. Their really nice Home and Garden Information Center website provides information for investigating plant problems.

 

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