Hi Master gardener,
i’m still not clear if I should be pruning them to the ground
You are not alone in wondering when to prune your Annabelle Hydrangea (H. arborenscens ‘Annabelle’ ). Unfortunately, there isn’t a quick answer. There are several schools of thought on when or if its even necessary to prune them at all. The most important thing you should know is that Annabelle Hydrangea bloom on new wood. It means they grow and set buds the same year they bloom. In your case that means new growth will appear in the spring of 2018 with blooms appearing in mid-summer on that new growth.
Gardeners really like Annabelle hydrangeas because they bloom every year regardless of how they are cared for or treated. It is a good idea, however, to prune these shrubs if they grow too large for their space or are unruly and need tidying up.
These shrubs are vigorous bloomers, and definitely can handle aggressive pruning. They will bounce back with beautiful flowers. In theory you can prune way back but not completely down to the ground level in the Fall. It would be better to leave 3-4″ of stem if you do an aggressive prune. This is supposed to encourage vigorous new growth. Bear in mind though, that if you continually cut right back it can, in time, weaken the plant and branches holding the blooms may need staking.
In a previously written Toronto Master Gardener article posted April 26, 2013 we suggest:
“… late winter or early spring is the [best] time to prune. Just look for the first set of fat new buds and prune back the stem to just above this new growth. If you have a lusty plant and want to keep it contained, you can cut back drastically — almost to the ground — in late winter before the new growth appears. Or you can leave more of the woody stem in order to give the heavy heads more support. Cut any dead branches to the ground at any time; they’ll be brittle, so easy to identify…”
Pruning in late winter or early spring when bare branches of the plant are exposed make it easier to carry out the necessary cuts. Some gardeners prune to rejuvenate an older plant. This can be done every 3-5 years. If you remove several of the oldest stems by 1/3rd, take out dead, broken, diseased and crossed branches it will produce a much healthier plant. Pruning back some of the branches to 18-24″ provides a sturdy framework for supporting new blooms.
Whatever you do avoid pruning right before your plants are about to bloom. Remember to use good quality pruners and make sure they are clean and sharp.
For more information on your plant visit the Toronto Master Gardener website at www.torontomastergardeners.ca and conduct a search for ‘hydrangea’ or ‘Annabelle hydrangea’. You will be directed to several posts.