We found Pin Cherry (Prunus pensylvanica) in several locations on our field trips but mainly within one specific habitat. Since Pin Cherry enjoys sunlight and open areas it can often be found along the edge of a forest and field or clearing. We found Pin Cherry at the Lingan Wind Farm, near North Mountain Beach in Neil’s Harbour, and along the Northside East Bay trail, among other places. The black lumps we refer to as Black Knot resembles a charcoal-like gall is actually a fungus! It can be found upon cherry, chokecherry, plums, and prunes. In our case we viewed it occurring on Pin Cherry. The lumps of Black Knot are a fungus (Apiosporina morbosum) which acts a parasite and feeds upon the tree and disfigures it. The symptom of this infection does not become apparent until the winter of the second season after the tree has become infected. The infection can sometimes occur as early as 20 months before signs of growth become apparent. The symptoms of an infected tree appear as tiny galls on the branches or as swellings of the shoot tissue. This gives the shoot a cork-like appearance. Once the infection has set after the second winter and it enters its second season, the knots develop quickly. If you ever notice black knot appearing to have a white or pinkish tinge you may be observing another fungus developing on the older portions of Black Knot. The fungus develops when infection takes place during wet periods and the young green shoots and wounded tissues of the parasitized plant are the most susceptible to infection by the spores of the fungus. If any of your cultivated trees exhibit signs of developing Black Knot or Black Knot is already mature and present and you would like to remove it for aesthetic reasons and to save your trees you should know that the best time to remove the knots is in the winter which is prior to the release of spores.
Pin Cherry (Prunus pensylvanica) bark. Photo taken in Northside East Bay, January 2010.
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