Our ornamental cherry has lost leaves and blossoms have shriveled and small branches died in early spring for a few years and now only has blooms and leaves at the very tops of each main branch. We are in Zone 5b (Brampton) and the tree is in a sunny position, about 5 m tall. I sprayed it with a dormant oil/Sulphur spray this spring before blooming assuming that it had a fungus. This time, the blooms have lasted longer than last year. However, it is still very sparsely leafy, only at the tops. Would it benefit from a severe prune down to a few meters to start again or would that kill it?
Thank you for contacting Toronto Master Gardeners;
The photo shows a well planted prunus tree of the Rosacea family, which there are hundreds of varieties. Your tree shows a good central leader, good side branches, few branches having leaves. Fruit trees are pruned in late winter to remove any diseased that are broken, crossing, or to train shape branches, where only one third of the tree should be pruned. At this time of the year branches that are crossing/touching each other can be removed after blooming. Pruning any tree more than a third will cause it stress and decline.
Ornamental cherry trees are naturally short lived trees and in later years can succumb to many diseases: Armillaria fungal disease the most common disease, not visible to the eye as it is under the bark and only shows itself when the tree is ailing. Look under the bark for white, fan-shaped patches that are between the bark and the inner wood there is no cure for Armillaria. Gummosis is another disease that affects ornamental cherry trees, our website has information on cankers and Gummosis Cherry tree Gummosis & Canker . Another disease which I do not see on your tree is canker caused by fungal spores that enter the bark in vulnerable open wounds. Our website has information on fruit tree cankers: Canker growing on Peach and Chokecherry
If you decide to replace the tree our website has Planting a Tree for Life a Toronto Master Gardener Guide on how to plant Trees and Shrubs: