The 1 Pruning Mistake That Can Ruin Your Hydrangeas This Autumn

I'm taking notes, not nodes...
Galina Zhigalova via Getty Images

If you’ve got a garden, you’ll know that autumn is prime pruning season.

Whether you’re deadheading roses or hacking back your hedgerows (hopefully not too far!), ’tis the season for beheading lots of unsuspecting plants – they’ll be grateful for it someday.

But not all plants can, or should, withstand this treatment. Ivy, for instance, benefits wildlife much more if left untrimmed in winter; while cutting into evergreen plants and shrubs in the winter could potentially cause permanent damage.

And it turns out that when it comes to trimming, not all hydrangeas are created equally – old wood and new wood hydrangeas require entirely different pruning practices.

So, we thought we’d explain the difference between the two, how to spot them, and what to do for both.

It’s all about blooming windows

Hydrangeas that bloom on old wood “create their flower buds for the following year shortly after they finish blooming during the current one. In other words, the flowers are created on wood that is at least one year old,” experts say.

So, if your flowers bloomed in the past season, you’ve probably got old wood.

These can’t be pruned and should be left alone until spring, because as they bloom so early in spring, they need to form their buds in autumn before the cold weather kicks in.

This means if you chop off their buds now, they won’t have a chance to bring the buds back – it’ll be too cold and miserable.

“They simply wouldn’t have enough time to re-grow before short days and cool weather set in,” the pros at say. So, cutting their spring buds now would ensure you have no flowers the coming year.

New wood hydrangeas, on the other hand, grow buds in spring. They’re not out yet – so it’s fine to prune new wood hydrangeas in autumn, as there are no flowers to harm.

How can I tell the difference?

There are a couple of ways. Firstly, you can work out when your plant flowered – in general, the earlier into spring your hydrangea grows buds and blooms, the more likely it is to be an old wood plant.

If your hydrangeas flower for around nine months of the year versus a shorter two- to six-month period, you’re also more likely to be dealing with old wood.

And some hydrangeas always bloom on either old or new wood. Panicle hydrangea, smooth hydrangea, and bracted hydrangea blossom on new wood; while bigleaf hydrangea, mountain hydrangea, cascade hydrangea, climbing hydrangea, and oakleaf hydrangea are old wood flowers.

If in doubt, don’t prune. Though pruning can prevent woody plants, it’s not necessary for your plant’s survival; and cutting a developing bud accidentally could be ruinous.