Don’t Prune Hydrangeas Before Making This One Vital Check – It's Simple to Do, Even if You're a Beginner Gardener

Cool your jets and hang onto your hand pruners: this simple check is vital before you prune hydrangeas if you don’t want to risk losing a whole year’s worth of glorious blooms. While it’s true that many hydrangea shrubs should be pruned in late winter or early spring, some need to be left well alone. Chop the wrong ones, and you’ll snip off this summer’s flowerbuds and be left bloomless! But don’t worry: it’s easy to tell which to prune and which to leave till summer by making one simple check.

Which Hydrangeas Can I Prune Now?

Some hydrangeas produce their flowers on fresh new growth made in spring. These ‘new wood’ hydrangeas are the ones to prune at this time of the year, encouraging lots of fresh growth and therefore abundant flowers.

Other hydrangeas start growing their flowerbuds after they’ve finished blooming, in late summer and early fall, so they produce flowers on the ‘old wood’ grown the previous year. Prune these heavily in late winter or spring and you won’t have any blooms this year: they should have a trim when they’ve finished flowering in summer.

What's the Vital Check to Tell Them Apart?

If you already know the name of your hydrangea or kept the plant label safe, then check below to see if yours is a ‘new wood’ or ‘old wood’ hydrangea. No idea? You should be able to work out what type of hydrangea it is from the descriptions below. But your biggest clue is out in your garden, so go do this simple check right now.

All you need to do is take a close look at the stems for flowerbuds. If prominent, plump buds are already present on woody stems – there will likely be one at the stem end as well – in winter, you’ve got an old wood hydrangea. No sign of flowerbuds, or you can only see a few new buds on fresh green growth? Then you’ve got a new wood hydrangea.

It’s best to wait until after your last frost date, depending on your USDA zone, before pruning any hydrangea, but carry out this check before spring growth really gets underway, and it's far easier to tell if you have a new or old wood hydrangea.

Which Hydrangeas Bloom on New Wood?

Smooth hydrangeas (Hydrangea arborescens) and panicle hydrangeas (H. paniculata) both bloom on new wood, so need pruning in late winter or early spring.

The flowers of smooth hydrangeas are typically white, pink or green and mostly mopheads (spherical clusters of big petals) with a few lacecaps (an outer ring of large petals surrounding a centre of small flowers); their leaves are typically textured and relatively thin. ‘Annabelle’, ‘Invincibelle’ and ‘Incredibelle’ are all smooth hydrangeas.

Panicle hydrangeas usually have cone-shaped flowers that are white or pale green, and simple ovate leaves with a tapered tip. ‘Limelight’ and ‘Pinky Winky’ are popular cultivars.

How to Prune Smooth & Panicle Hydrangeas

Both new wood smooth and panicle hydrangeas can handle hard pruning, and it’s best to be brutal. In late winter or early spring, snip off around a third of last year’s growth, cutting just above a pair of strong-looking buds. This will encourage lots of fresh stems and, as the flowerbuds form on this new growth, plenty of flowers.

You should also remove any dead, diseased or damaged stems.

Aim to create a pretty-much permanent skeleton of healthy older branches, around two feet high, from which new stems grow each year. If your shrub is way bigger than this at the moment, gradually work towards this height over the next few years.

While new wood hydrangeas are forgiving plants, it's best to wait till after your last frost before pruning. Make the cut too early and all that new growth it encourages could be killed by the cold.

The Best Tools for Pruning Hydrangeas

Which Hydrangeas Bloom on Old Wood?

Bigleaf hydrangeas (Hydrangea macrophylla), oakleaf hydrangeas (H. quercifolia) and mountain hydrangeas (H. serrata) all flower on old wood, so don’t need pruning now.

Bigleaf hydrangeas usually have pink or blue mophead blooms and thick, waxy, textured leaves that are ovate or heart-shaped. Popular cultivars include ‘Nikko Blue’ and ‘Big Daddy’. Mountain hydrangeas are closely related so look similar, but are smaller and likely have flowers in lacecap form, and include ‘Blue Billow’ and ‘Blue Deckle’.

Oakleaf hydrangeas typically have white, cone-shaped flowers and their foliage is – you guessed it – shaped like an oak leaf. ‘Ruby Slippers’, ‘Pee Wee’ and ‘Snow Queen’ are a few favorite cultivars.

How to Prune Bigleaf, Mountain & Oakleaf Hydrangeas

These old wood hydrangeas shouldn’t be pruned much at all, rather given a light trim in summer once they’ve finished flowering. Then remove any dead, damaged or diseased stems, and snip off faded flowers. If there are any over-long stems, you can cut these back by up to one third, snipping just above a pair of healthy buds.

If you miss this pruning window, leave your shrub alone, otherwise you risk losing flowers the following year.

You can give these hydrangeas a tidy-up in early spring, too. Many people leave the faded flowers in place for winter interest, and to protect the already-formed flowerbuds from the cold. In that case, simply snip off the old blooms just below the flowerhead, being careful not to damage any buds. If there’s any winter damage, remove this too. It’s vital to wait until after your last frost though, as all that old plant matter helps insulate those all-important buds.

If yours is a mature plant, you can keep it invigorated by also removing an elderly stem right at the base. While this will remove some flowerbuds, you’ll encourage a new supply of fresh stems that will flower profusely the following year. So as long as you make this an annual task, you won’t notice the loss. But honestly? Even if you don’t prune an old wood hydrangea at all, it’ll be absolutely fine.

What About Reblooming Hydrangeas?

Those clever plant breeders have created reblooming, also known as remontant, hydrangeas that flower on both old and new wood. This creates two flushes of flowers, and ensures that, even if the old-wood buds are damaged by the winter chill, the plant still blooms. Only bigleaf and mountain hydrangea have these specialized varieties, and popular series include the Endless Summer, Summer Crush and Let’s Dance.

Treat rebloomers as old wood hydrangeas, removing only dead, diseased or damaged stems in late winter or early spring, deadheading spent flowers once they’ve faded through summer. You can also reinvigorate mature reblooming hydrangeas by occasionally removing an elderly stem at the base.

Still Scared to Prune Your Hydrangea?

Even if you prune an old wood hydrangea in spring, you won’t kill it: the worst case scenario is that you don’t get any flowers this summer. And if you don’t prune a new wood hydrangea? It’ll be absolutely fine too, you'll just get fewer flowers and some droopy stems.

But do scribble a note in your calendar or gardening journal to ID your hydrangea species in summer when it’s in full bloom. Inspect it in late fall, too. At this time of the year, you can easily see if flowerbuds are forming in the leaf axils (where a leaf joins the stem) and on the stem end, so you’ll know for definite if it’s an old or new wood hydrangea and can wield your hand pruners with confidence next year!