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Q. Who is Mr. Smarty Plants?

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Sunday - August 01, 2010

From: Mt Pleasant, MI
Region: Midwest
Topic: Shrubs
Title: Dogwood under a black walnut in Mt.Pleasant MI
Answered by: Barbara Medford

QUESTION:

Can I grow red or yellow twigged dogwood near a black walnut?

ANSWER:

You can plant a Cornus sericea (redosier dogwood) anywhere you choose; whether it will thrive or even live more than a year or so under a Juglans nigra (black walnut) is another question entirely. Both are native or near your area of Isabella County, in central Michigan, USDA Hardiness Zones 4a to 5a.

The problem, as you may know, is a characteristic of black walnut to emit juglones, substances intended to discourage or prohibit competition from other plants. We found an excellent article from  Virginia Cooperative Extension Black Walnut and Allelopathy which fully explains this procedure. Even plants some distance away can be affected because every part of the tree exudes the juglones, including roots which may extend 3 times the size of the crown. However, this same article had a chart of plants that were resistant to the effects of allelopathy, including trees and shrubs. On this chart of resistant plants "dogwood, flowering" was listed. There are 14 members of the genus cornus, dogwood, native to North America, and all of them appear to us to be flowering including Cornus sericea (redosier dogwood).

Therefore, we are assuming that it would indeed be okay to plant the dogwood in the area of the black walnut. If the dogwood does fail to thrive, you can always blame moles or bugs or too much rain or too little rain, just don't blame the researchers or Mr. Smarty Plants. 

From the Native Plant Image Gallery:


Cornus sericea

Cornus sericea

Juglans nigra

Juglans nigra

 

 

 

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