I have many of these Nikko Blue and Endless Summer hydrangeas at my home in Waterdown, Ontario. Last year they put on a beautiful show and my niece asked me to supply many buckets-full of flowers for her August wedding last summer which I did. I believe that this variety blooms on the previous year’s stalks so I never prune them in the fall or spring. This year I had only 1 or 2 blooms on each of the bushes. Why didn’t I get any flowers this year? The plants look very healthy. I put some Miracle Grow slow release pellets around the base in the spring. Am I supposed to prune them? If so, when? Many thanks for your help.
Thank you for contacting Toronto Master Gardeners regarding your hydrangeas (Hydrangea macrophylla) that produced only a few blooms this year.
‘Nikko Blue’ hydrangeas bloom on the previous year’s growth, while Endless Summer® hydrangeas bloom on the current year’s and previous year’s growth. In the case of both cultivars, several factors can impact blooming, including winter conditions, pruning practices, over-watering and over-fertilizing. It is very likely that winter conditions and pruning are the culprits here.
In areas where winter temperatures reach or go below freezing, there is a risk of flower bud loss, since buds form primarily in late summer and early fall of the previous year. For this reason, it is recommended that you do not prune or cut back the hydrangeas after August 1 and, if possible, leave fall blooms on the plants over winter (see more information here). The combined effects of cutting (aka pruning) buckets-full of flowers for your niece’s wedding in August of last year, followed by a record-setting cold winter, likely resulted in your hydrangeas having little to no flower buds this year. You might see some flowers yet on the Endless Summer® hydrangeas, as they may still produce blooms on this year’s growth. Either way, your plants will very likely resume their colourful show next year, once they have had another season to form flower buds.