Yesterday, I took 20 minutes to prune my Annabelle hydrangea.
Annabelle is a popular cultivar of our Illinois native smooth hydrangea aborescens, a hardy mophead with huge, heavy heads of blooms that offers a beautiful cloud of white for months in June and July. It prefers part-shade but can tolerate full sun happily (with good moisture).
You don’t actually have to prune it at all, but Annabelle (and other aborescens hydrangeas) bloom on new wood (as do the panicle hydrangeas), so if you don’t prune, over time, you’ll build up a real thicket of old wood with a relatively low ratio of flowering stems.
Annabelle is tough — if you really want to, you can chop it all the way to the ground, and it’ll come up from there. But that’s hard on the plant, and will weaken it over time, especially if you do it year after year.
Plus, Annabelle is so top-heavy that its blooms often drag the ground, especially after it rains. If you leave some of the old wood, it’ll act as a support, and help prevent the flopping. I also use a metal support (from Gardener’s Supply, linked below — it’s held up well for close to a decade now).
Another approach is to plant 3 or more Annabelles in clumps close to each other, so they support each other. (If you’re planting a new shrub, you might look at a cultivar instead, Incrediball, which has large blooms on very strong stems, that are able to hold the flowers upright.)
Here’s what’s recommended for pruning Annabelle:
a) remove spent flowerheads either right after bloom, or in early spring, if you’ve left them for winter interest (I always do — I think they look lovely topped with little peaks of snow, or iced with frost)
b) remove up to a third of the branches, pruning those close to the ground. You can see here that I’ve chosen to mostly remove the exterior branches this year — I use a frame to support Annabelle, so that gave me an easy guide for where I’d prune
c) prune remaining branches to 18-24″ from the ground; I pruned back branches that extended outside the top of my support frame, more for neatness and shape than anything else. Again, none of these remaining branches will bloom again.
Soon, those old branches will green up, and the new branches will emerge, and before too long, we’ll have lots and lots of pretty green puffs which will slowly turn glowing white. In late summer, they’ll start fading to tan, and will happily stick around to provide fall and winter interest.
The story of Annabelle: https://extension.illinois.edu/…/showy-annabelle…
Jardin bird cage support: https://www.gardeners.com/…/jardin-bird…/39-521.html…