I love Bigleaf Hydrangeas (H. macrophylla), the traditional garden Hydrangea with either big mophead flowers or the subtler lacecap flowerheads. Most gardens have a Hydrangea or two tucked in, and why not? As long as they have composty soil and get watered regularly, they make a fantastic show of blooms with very little effort on our part.
It’s coming up on the time of year to prune them in warmer climates where it doesn’t snow (right after they finish blooming is best), and I made a video and took some photos to show you how (if you live in a colder climate, you use the same technique to prune, only you’d do it in mid-spring to protect against frost damage).
Why prune? Scientific studies have shown that Hydrangeas that are pruned properly flower more than plants that are left unpruned. Pruning also encourages a fuller habit for the shrub and stimulates the new growth that keeps the plant healthy.
The video shows you how to do it, but here’s the basic idea:
|Before pruning cut is made – look for swollen buds||After pruning cut is made, just above swollen buds|
When you are ready to prune off your dead flowerheads, look along the stem for a pair of swollen buds at the base of each leaf. The first set of leaves below the flower rarely has these swollen buds, but often the second and third pair of leaves do.
Prune off every dead flowerhead to just above these swollen buds, taking care to leave the buds unharmed when you cut. Once you’ve cut off every dead flower to a part of the stem that has these swollen buds, stand back from the shrub and notice whether there are any shoots sticking up above the rest of the plant. Feel free to prune any of the other, non-flowered shoots to their own sets of swollen buds to give the plant an even, rounded shape.
After you’ve pruned the entire shrub in this way, you can look inside the shrub to see if you want to remove any of the oldest branches which are least likely to flower. If you remove one quarter of the oldest, woodiest branches each year by pruning them out as far down as you can, it keeps the plant rejuvenated and ready to put out fresh young stems which will flower more for you.
You can also prune out any stems that are so spindly they wouldn’t hold up a flower, and any stems that are dead with no leaves. I love to do this kind of regenerative pruning at the end of the summer when you can still see what stems are alive. Once the plant loses its leaves for winter, it’s harder to tell what’s dead.
If you’re a fan of Hydrangeas like I am, you might enjoy Michael Dirr’s book about them. Hydrangeas for American Gardens profiles the most common types of Hydrangeas available, and shows off some unusual varieties as well. Some of the language in the book is a bit stiff and scientific, but Dirr keeps his sense of humor, too. I love this sentence where he’s discussing watering:
Hydrangea macrophylla, more so than any other species, will signal when drought-stressed, with leaves drooping like a scolded dog.
So true, Michael!!
Edit April 2010: Debbie over at Garden of Possibilities has just written an excellent article on pruning Hydrangeas if you live in a colder climate. Check it out!