Endless Summer Hydrangea (Mopheads)

(Question)

I have 10 Endless Summer hydrangea plants (7 are over three years and three are over one year). Only two had blooms this year. Last year all but one had A LOT of blooms. I live in Ottawa and we had mild weather in March then a short cold period. Can you tell me why my plants may have not bloomed this year? Do I need to winterize them somehow? Last year I did put about four inches of oak leaves around the base of all the plants to protect them from the snow. A garden center told me last fall that I should cut the plants down by a third in the spring. I did this and thus no blooms. Should I leave the plants alone altogether – no pruning fall or spring? Should regular fertilizing 10-30-10 help them next year and how often should this be done? Any advice you could give me would be appreciated. I am so disappointed with no flowers this summer. Thank you.

(Answer)

The problem is most likely that you cut them down in the spring. This is a mistake according to the website of The Endless Summer Collection at https://endlesssummerblooms.com/en/consumer/plants/bloomingsuccess   which says “Don’t treat your Endless Summer Hydrangeas like an Annabelle Hydrangea by cutting them back in the fall or early spring. By cutting to the ground or within a few inches of the ground, most if not all of the buds on old wood are being removed. ..Endless Summer Hydrangeas certainly do bloom on new wood, but it may take longer for flower buds to develop on the new growth of a young plant.”