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Oozing Trees

April 30, 2003

Nearly a month ago, I looked out the window at my favorite pagoda dogwood to see a wet trail seeping from the trunk. I thought this was merely the pattern of drying from a recent rain. Several days later, the seeping continued and convinced me that the tree must have a canker disease and that it might decline this season. Unfortunately, pagoda dogwoods in our area usually do become infected with canker fungi, which starts the mortality spiral leading to death. I spoke to several specialists about this seeping and found an interesting article in the Morton Arboretum newsletter, The Plant Health Care Report, www.mortonarb.org/plantinfo/index.htm. My tree may have a canker problem, but I was relieved to know that other apparently healthy trees were showing the same phenomenon.

According to The Plant Health Care Report, George Ware, a well-known and respected dendrologist, explains that the xylem in thin-barked trees heats up quickly, sometimes causing sap to be exuded from weak or injured areas in a tree in late winter or early spring. The seeping I observed coincided with record-high temperatures, so I suspect that Ware’s description is correct for my tree. If you see similar symptoms on your thin barked trees, do not panic. This is most likely a harmless occurrence. Still, you might want to pamper such trees to help them thrive this year.

Although similar, this condition is not bacterial wetwood or slime flux. I did not see any oozing in the known wetwood-infected trees in our area. For infor-mation on wetwood, consult Report on Plant Disease, no. 656, “Bacterial Wetwood and Slime Flux of Landscape Trees,” available on the Extension VISTA Web site or in local Extension offices.

Author: Nancy Pataky


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