Quick answer

On the commonest UK hydrangeas, the mopheads and lacecaps, leave them alone. Next summer's flower buds are already on the stem just beneath each faded head, and cutting now removes them. Wait until those buds visibly swell in spring, usually late March to April, then cut back to the first strong pair.

The honest answer to what to do with hydrangeas after flowering in the UK is to put the secateurs down. A September tidy-up is the most reliable way to end up with a hydrangea that makes plenty of leaf and no flowers next summer.

Not every hydrangea works that way, which is why this starts with identification rather than a date. Two of the types you are likely to meet can be cut back hard without losing a thing. The rest cannot.

Table of contents

Start by working out which type you own

You do not need a plant label. What settles the answer is visible from where you are standing: the shape of the faded head, the feel of a leaf, and whether the plant clings to a wall.

Mophead: a dome of florets and thick, glossy leaves

A round head the size of a grapefruit, made entirely of showy florets with nothing fertile in the middle, over thick, glossy leaves. This is Hydrangea macrophylla, common in UK gardens and the one that punishes an autumn haircut.

Lacecap: a flat plate with a fuzzy centre

The same species wearing a different flower: a flat head with tiny fertile flowers in the middle ringed by a few large showy ones, on leaves indistinguishable from a mophead's. Lacecaps are slightly hardier and may be deadheaded straight after flowering, cutting to the second pair of leaves below the head, but that window shuts in early August so anything later waits for spring. Hydrangea serrata, the mountain hydrangea, is a scaled-down version with narrower leaves and takes the same treatment.

Panicle: a cone rather than a dome

A long cone tapering to a point, aged from white to dusty pink, on smaller matt leaves with no lobes, often in threes around the stem. Hydrangea paniculata is common here and much the most forgiving, because it flowers on growth made the same year.

Annabelle and the smooth types: white globes on slender stems

Big spherical heads of white fading to papery beige mark out Hydrangea arborescens, usually sold as 'Annabelle'. The leaf is softer and more heart-shaped than a mophead's, on slim stems that bow under a wet head.

Climbing hydrangea: it holds itself to the wall

Self-clinging growth that grips brick or bark, under flat white lacecap heads, means Hydrangea anomala subsp. petiolaris. It flowers mainly near the top, and a shady north wall is where you find it.

Oakleaf: lobed leaves turning crimson

Lobed foliage shaped like oak leaves, colouring from pink to deep purple, gives Hydrangea quercifolia away at a glance. Its flowers are cones like a panicle's, so the leaf tells them apart. It is far less common here, and hardy to around -15C.

That is the split that decides everything below. Mophead, lacecap, mountain, oakleaf and climbing types carry next summer's flowers on wood that already exists in your garden today. Panicle and smooth types build theirs from scratch each spring. Cutting the first group now costs a season, with climbers the one exception: their window is July and August, straight after they finish. Cutting the second group costs only the winter silhouette.

The case for leaving the faded heads on

A mophead sets next summer's flower buds in late summer. They are on the stem right now, a few centimetres below each browning head, and they have to survive every frost between today and April. That is why this shrub is fussier than anything else in the border.

Standard UK practice is to leave the dead heads as a rough cap over those buds. The RHS puts it carefully, saying they offer "some frost protection for the tender growth buds below". Gardeners' World adds a mechanism: hydrangea stems are corky rather than woody and hold moisture that can freeze, so a freshly cut stem is the one at risk.

Sources do not fully agree on how much difference this makes. The RHS itself concedes that in mild areas the heads can come off as soon as they fade, and a dry flowerhead is a poor insulator, which is why the practice is often defended as winter interest instead. Nobody publishes bud-survival numbers.

We would leave them on, and not because the evidence is settled. Leaving them costs a scruffy shrub for six months; getting it wrong costs a summer. In a cold or exposed garden that asymmetry is not close; in a mild coastal one it is your call.

Month by month, from late summer to spring

Dates in UK gardening are a starting point, never an instruction. First frosts reach inland Scotland weeks before a Cornish coast, a frost pocket runs two to three weeks ahead of the ground above it, and a south-facing wall shifts things again. Work from your own garden's frost history.

Late August and September

Nothing needs cutting on the shrubby types, and this is when most people reach for the secateurs and lose next year's display. Climbers are the exception: pruned straight after flowering, so late August is the tail of their window and anything left waits until next summer.

Take semi-ripe cuttings instead: hydrangeas root readily from 10 to 15cm of this year's growth, firm at the base with a soft tip. Cut just below a node, strip the lower leaves and the tip, and set them in half peat-free compost, half sharp sand. Cover the pot with a clear bag or use a propagator, and keep it warm and light but out of direct sun.

It is also the last sensible moment to cut heads for drying: wait until they feel papery rather than soft, then stand them in a vase holding a little water until it evaporates. Stop feeding, because nitrogen this late pushes soft growth that cannot harden off before the first frost.

October

Leaves colour and drop, heads turn to a papery buff, and there is still nothing to cut on the old-wood types. Rake fallen leaves off the crown if they are sitting wet against the stems.

November and December

First frosts arrive across most of the country. Mulch now, 5cm of garden compost or bark over the root area, kept clear of the stems. Containers are the weak point, because roots in a pot freeze as roots in open ground do not, so move them against a house wall.

January

Do nothing beyond checking the ties on anything trained, and firming the soil around any young plant the wind has rocked loose.

February

For a mophead the answer is still not yet: February and March frosts are the ones that catch swelling buds. Panicle and smooth types can be cut from late February, because none of the wood they will flower on has grown yet.

March and April

Now, for every type except the climbers, which wait until they have flowered. The buds low on each stem swell and begin to break, which is the signal missing all winter, because it shows where the live wood ends. In a mild southern garden that is often late March; further north, mid to late April is normal and waiting costs nothing.

Making the spring cut, step by step

Pick a dry, still day with no hard frost forecast for the week ahead. Sharp, clean blades matter more than expensive ones, because a crushed stem heals slowly.

1. Wait for the buds, not the date

Start on the old-wood types: run a thumb up a stem from the base. Live buds are plump, green-tipped and springy; dead wood is dry, hollow-sounding and snaps instead of bending. Cut nothing there until you can see buds swelling, or you are guessing where the live wood ends. Panicle and smooth types skip this gate and can go any time from late winter.

2. Cut each old head back to the first strong pair of buds

On mopheads, lacecaps, mountain and oakleaf types, follow the stem down from the brown head to the first fat, healthy pair of buds and cut straight across about 5mm above them. The buds sit in opposite pairs, so a sloping cut dries out the lower one. Climbers are the exception and are pruned in summer, straight after flowering, not now. A hundred cuts is hard on the hands, and a ratchet mechanism splits each into several squeezes.

3. Take out one or two of the oldest stems at the base

An established macrophylla also wants one or two of its thickest, greyest stems cut down to ground level every spring, which keeps it making young wood instead of a thicket flowering top-only. Renovating the whole plant by cutting every stem to the base works too, at the cost of that year's flowers.

4. Cut panicle and smooth types much harder

These want a permanent low framework. Cut last year's stems back to a pair of healthy buds on that framework, or, for fewer but much larger heads, down to the lowest pair of buds at roughly 25cm.

5. Clear up and feed

Rake the old heads and prunings out of the base, where they hold damp against the stems. One general-purpose feed in spring is plenty: excess nitrogen buys leaf at the expense of flower.

What goes wrong, and how to recover

A shrub full of leaves and no flowers

Rule out the alternatives before blaming the secateurs: a late frost on the buds, too much shade and too much nitrogen all produce the same shrub, and none is cured by waiting. If it really was an autumn or winter cut on an old-wood type, there is no rescue for that season: leave the plant alone, cut nothing until the following spring, and it comes back.

New shoots blackened by a late frost

April and May frosts scorch soft new growth, and the shoots go limp and brown within a day or two. Wait until no more frost is expected, then cut to an undamaged bud or sideshoot and top-dress with a general fertiliser to drive the re-growth. Cutting inside the frost window only feeds the next.

Heads that went slimy instead of papery

A wet autumn can rot faded heads, and a sodden head pressed against a bud does more harm than good. If they have turned to mush rather than paper, take them off and mulch more thickly.

A climbing hydrangea pruned at the wrong moment

If you have missed the July to August window, leave it until next summer. A hard spring cut typically costs two summers of flower, so reduce an overgrown plant in stages over three or four years.

Frequently asked questions

Should I deadhead my hydrangea in September?

No, not on a mophead. The buds for next summer sit just below each faded head, and the heads shelter them through the winter. Lacecaps can be deadheaded after flowering, but that window closes in early August, so by September leave them.

My hydrangea has cone-shaped flowers. Can I cut it in autumn?

Check the leaves first, because two types carry cones. Matt leaves with no lobes, often in threes around the stem, mean a panicle hydrangea, which flowers on shoots it has not grown yet, so an autumn cut costs no blooms, though we would still wait for late winter. Lobed, oak-shaped leaves that colour crimson mean an oakleaf, which flowers on old wood and must be left until spring.

What should I do if I already cut mine back in September?

Stop there and do not cut it again. On an old-wood type you will probably get plenty of leaf and few or no flowers next summer, though the plant will be healthy. Leave it unpruned through the following autumn and it flowers on schedule the year after. If the aim was to shrink it, do that in spring.

Do I need to wrap my hydrangea for winter?

Not in most of the UK, where garden hydrangeas take an ordinary winter unprotected. A container is the exception, because the roots are the vulnerable part rather than the top: move the pot against a house wall, or wrap the pot rather than the plant.