Why did my hydrangea not flower this year?

The four causes in order of likelihood — wrong-time pruning, late frost, too much shade or too much nitrogen — and how to tell which one it was.

Difficulty: beginner
Time: 20 min
Read: 3 min

Short answer

On a mophead, it is almost always pruning at the wrong time or a late frost killing the buds, because the flowers were already formed on last year's wood. Look at the stem tips: cut ends mean pruning, brown shrivelled buds mean frost.

A hydrangea that produces plenty of healthy leaves and no flowers is not unwell. Something removed or killed the flower buds, and the plant is doing exactly what it should with what it has left.

Step by step

Check whether it flowers on old or new wood.Mopheads, lacecaps and climbing hydrangeas form their buds the previous summer. Paniculata and arborescens form them in the current spring. Only the first group can lose a year's flowers to winter events.
Look at the stem tips.Clean cut ends mean it was pruned. Brown, shrivelled buds still attached mean frost. Fat green buds with no flower yet means it is simply early.
Rule out autumn tidying.Cutting the old flowerheads off in autumn removes the frost protection and often the buds themselves. Leave them until early spring.
Consider a late frost.A hard frost in April or May after the buds have started into growth kills them outright. Nothing can be done retrospectively; fleece over the plant on a forecast frost prevents it.
Assess the light.Hydrangeas flower poorly in deep shade. Dappled shade or morning sun with afternoon shade is ideal; a north-facing wall under a tree canopy is often too dark.
Check what you have been feeding it.Lawn feed drifting into the border, or a high-nitrogen general feed, produces vigorous leaf at the expense of flower. A high-potash feed in spring encourages flowering.
Check the water supply.Drought stress in summer, when next year's buds are forming, reduces flowering the following year. Hydrangeas are among the thirstiest shrubs in a UK garden.
Consider its age and how it was moved.A recently planted or recently moved hydrangea often skips a year while it re-establishes. This resolves itself.
Change one thing and wait a year.These plants respond over a full season. Stop pruning it, protect it in late frost, feed with potash in spring, and judge next summer.

Tips

Leaves fine, no flowers, means the buds were lost — not that the plant is ill.
Cut ends at the stem tips are the fingerprint of wrong-time pruning.
Fleece over the plant on a forecast late frost saves a whole year of flowers.

Common mistakes

Feeding harder to encourage flowers — Most general and lawn feeds are nitrogen-dominant, which drives leaf growth and suppresses flowering. Potash is the nutrient associated with flower and fruit.
Cutting it back hard in frustration — On a mophead that guarantees another flowerless year, and often two, because you have removed the wood that would have carried the buds.

If it doesn't work

Cut stem ends, no buds

Cause: Pruned after flower buds formed — Fix: Prune only in early spring, taking each stem back to the first fat pair of buds.

Brown shrivelled buds at the tips

Cause: Late spring frost — Fix: Cut back to live buds. Cover with fleece on frosty nights next spring.

Lush leaves, tall growth, no flower

Cause: Too much nitrogen or too much shade — Fix: Stop nitrogen feeding, apply sulphate of potash in spring, and consider moving it to brighter shade.

Flowered well then stopped after being moved

Cause: Transplant establishment — Fix: Water well, mulch, and expect normal flowering to resume within two seasons.

Questions people ask

Will it flower next year?

Almost certainly, if you leave it alone over winter, prune only in early spring, and protect the buds from a late frost.

Should I move it into more sun?

More light helps flowering, but full afternoon sun scorches hydrangea leaves and increases wilting. Morning sun with afternoon shade is the target.

Does the type matter?

Very much. Paniculata and arborescens hydrangeas flower on new growth each year, so they rarely miss a season. It is mopheads and lacecaps that lose whole years.