I live in London Ontario. I love mophead Hydrangeas but have not had good luck with them. I have read a lot and tried to follow all the rules re pruning etc. This year I notice a lot of mopheads flowering in my area.
Could you advise me which ones are most likely to rebloom? for example the Let Dance Series, Endless Summer?
Thank you for contacting Toronto Master Gardeners.
When choosing Hydrangeas it is important to know there are two different kinds. One type blooms on new wood so if the hydrangea has died back during the winter this is not an issue for blooming the following year. In the spring new growth will emerge and buds will develop and bloom on the new shoots. the second type blooms on old wood. This means the buds are set in the fall and if they are damaged in the winter or there is any die-back of the branches, there will be no blooming the following year. Most of these will only bloom occasionally in Ontario as our winters can be a bit harsh for them
When you are choosing a plant you need to know if you are choosing one that blooms on old or new wood. You can ask at the Nursery. If they do not know, a quick google to a reliable site should give you your answer. There are new varieties coming out all the time and some are now developing the ability to bloom on new and old wood. Once you know how they bloom, pruning becomes an easier matter. If they bloom on old wood you need to prune them right after blooming. If you prune them in the fall or spring you will remove the buds for the next blooming season. Ones that bloom on new wood can be pruned in the spring so you can enjoy the left over blooms in the winter.
The typical Mop-head/large leaf hydrangeas that you see at all the stores in the late spring bloom on old wood so you are probably getting a plant that will only bloom once unless there is a mild winter. Also of note, the blue ones will probably turn pink over time as we do not have the acidic soil to maintain the blue colour. I have seen some new versions that can bloom on new wood as well but I do not know if they are available in Ontario.
Lacecap and Oakleaf hydrangeas also bloom on old wood.
The Annebelle and Peegee varieties usually bloom on new wood so will have a much greater chance of performing well in the garden. A variety that appeared a few years ago that I have had tremendous luck with is Hydrangea paniculata ‘limelight’.
The ‘endless summer’ and ‘lets dance’ say they bloom on both old and new wood. They maybe an option for you. ‘Endless summer’ does say zone 4-9 which is promising.
I have added some links below for information on various Hydrangeas for further reading.