One of the questions that we get asked most commonly is “when to prune Hydrangeas”. Following this as a close second is “why didn’t my Hydrangeas bloom this year”. It can seem a bit confusing, so let’s simplify things.
I am sure that many of you, at this point, feel that if you do not prune your hydrangeas under full moons while uttering a mythical incantation, your Hydrangeas will no longer bloom. Hopefully this article can help remove the mystique of Hydrangeas and you can have your plants blooming beautifully for next season.
Hydrangeas can be divided into two categories:
- those that bloom on NEW WOOD (current year’s growth)
- those that bloom on OLD WOOD (last year's growth)
The Hydrangeas that bloom on OLD WOOD are from the macrophylla family. These include Nikko Blue, Endless Summer and many other pinks and blues. When we say they bloom on old wood we mean that they are busy right now (August and September) setting flower buds for next summer. So next year when they take off growing in the spring, the flower shoots will actually emerge from the older wood, the wood that was produced this year.
The hydrangeas that bloom on NEW WOOD are typically the white Hydrangeas like Annabelle and Paniculata Grandiflora (PG). They put on new growth in the spring and the flower buds bloom the current year. That's why the Annabelle and PG are such prolific bloomers. They set flower buds and almost immediately those buds produce big, beautiful, abundant flowers. Annabelle and PG Hydrangea can be pruned during the late fall, winter or early spring. Once they start growing in the spring they do not need any pruning until after they bloom. Almost nothing can go wrong with their blooming sequence!
But with the Blue and Pink Hydrangeas (macrophylla) all kinds of things can go wrong with the flower buds. They bloom on OLD WOOD. Since the flower buds are produced in August and September they have to make it through the harsh winter before they can bloom. The flower buds can be damaged by extreme cold. Pruning? You should prune macrophylla Hydrangeas right after they bloom in September, before they have a chance to start making new flower buds.
One of the most popular new varieties on the market is "Endless Summer Hydrangea" and it is known to bloom more than once in a season. It's in the macrophylla family and sets flower buds on old wood, but it is also known to set more buds and produce flowers during the growing season. It should still be treated as a Hydrangea that blooms on old wood.
So . . . with all of that said, if your Hydrangea did not bloom then the flower buds might have been pruned off, the flower buds were damaged over the winter or the deer ate them! Don’t be discouraged, ANY Hydrangea is worth the fuss!
Integral Tree and Landscape