You’ve seen them along Scurfield Boulevard, Columbia Drive and other residential streets in Whyte Ridge: the tarry black blobs attached to ‘prunus virginiana’ or, more commonly, Schubert chokecherry.
They weigh down the slender branches, looking like charred hot dogs on a campfire stick.
As new housing developments sprung up during the 1980s and 1990s, this variety of ‘prunus’ was the go-to tree for boulevards and property lines. The Schubert was relatively quick growing, they gave spring blossom, had interesting leaf colour — green changing to dark purple — and provided a good summer canopy. But they were monocultures, ripe for disease.
The fungus, Apiosporina morbosa, disperses spores in the spring through wind, wet weather and birds. By the next season, black galls or knots have formed and, if not treated, will continue this process both internally and externally, blocking the path of tree nourishment.
In the case of a single affected tree, pruning out the affected branch at least a foot above the gall may have the desired effect. But when the disease is rampant in trees standing side by side, as in Whyte Ridge, it is virtually impossible to control. Despite annual pruning efforts to keep the disease in check, I’ve lost the battle with my boulevard tree. Restricted and weakened by the galls, the tree has become susceptible to other diseases and insects. It is now starting to die. Others in the area are already dead.
In hindsight, we shouldn’t have taken it upon ourselves to prune our chokecherry. Only trees planted by the property owner are allowed to be pruned or removed. Martha Barwinsky, the city forester, stated that the City of Winnipeg has concise guidelines for the processes to be followed in regards to trees on their property. This information can be found at http://winnipeg.ca/publicworks/Forestry/Homeowner_Tree_Maintenance_Guidelines.asp
The positive news is that there is a Winnipeg Urban Forest succession plan. Barwinsky says the diseased and dying trees will be removed and replaced with more desirable specimens. Rather than a monoculture, the strategy now is to have no more than 30% of one variety of tree in a given area, creating a more diverse urban canopy and ensuring the health of individual trees. The timeline for replacement is undetermined.
If your Schubert chokecherry is struggling, call the Urban Forest Department (through the 311 line) and voice your concern. The squeaky wheel may get some grease and we may get some new trees.
Pat Kelly is a community correspondent for Whyte Ridge.