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.