I live in Scarborough in the GTA. This plant has been like this for at least 2 years. There is no problem in early spring when it is growing leaves but later, the flowers definitely are destroyed. Please help.
Your Hydrangea is indeed a sight for sore eyes. In general, damage could be caused by one or more of a list of pests that add hydrangeas to their diet – Aphids, Rose Chafer Beetles, Spider mites, Snails, Slugs, Thrips or Scale insects.
Take a close look at your plant and look for some of the telltale signs of infestation below:
Aphids – sticky honeydew on leaves that turns blackish with a fungus.
Rose Chafer Beetles – skeletonizing of leaves and holes on bloom petals.
Red & Two Spotted Spider Mites – fine webbing built between and on the undersides of leaves.
Snails & Slugs – silver trail left on leaves.
Thrips – tiny black waste dots appear on the flower petals.
Scale – small waxy/fuzzy insects or eggs on the leaf undersides or stems.
For Aphids, Chafers, Spider Mites and Thrips – treat with insecticidal soap and a good strong water stream/blast from a hose. For Scale insects, it is best to cut out any infested areas now before the winter and then use a spray of horticultural oil in the spring just before the leaves unfurl. For Slugs & Snails, hand picking off as many as you can now before they start to overwinter in garden debris or soil. A good clean up of any fallen leaves, branches or mulch around the plant is advisable to remove any hiding places. In the spring, sprinkling diatomaceous earth around your plant will help keep them at bay but this must be done several times during the growing season to maintain the barrier.