Quick Answer
Prune lavender in the UK in late August or early September, immediately after flowering, while the weather is still warm. Cut back the current year’s green stems to about 2cm above the old wood, but never cut into the old brown woody base itself. Lavender does not regrow from old wood, and cutting too hard will kill the plant.
Get the timing and the depth right, and a lavender will keep its neat dome shape for 8-10 years. Get either wrong and you end up with a leggy, hollow, woody mess within three seasons. Here’s the full method.
The Cardinal Rule: Never Cut Into Old Wood
This is the single most important thing to know about pruning lavender, and it catches out almost every new gardener.
Lavender does not regrow from old brown woody stems. Unlike roses, buddleia, or most shrubs, where you can cut back hard into old wood and expect fresh shoots, lavender simply will not produce new growth from the bare brown framework at the base. Once a stem is woody and leafless, it stays that way.
This means every prune has to stay within the soft, green, leafy part of the current year’s growth. The moment you cut below that line into the old wood, that section is finished, it won’t produce leaves, flowers, or anything else.
You can usually see the line clearly: the top half of the plant is green, leafy and flexible; the bottom is brown, bare and stiff. Keep the cut in the green.
When to Prune Lavender in the UK
Main prune: immediately after flowering, late August or early September.
The timing matters for two reasons:
- The plant needs warm weather to heal the cuts and put on a small flush of new growth before winter
- Pruning any later and those fresh cuts are exposed to autumn damp and frost, which causes dieback
A good target is two to four weeks after the last flowers have faded. For most English lavenders (Lavandula angustifolia) in Surrey and Sussex, that’s the last week of August through the second week of September.
Optional spring tidy: March or April.
A light trim in early spring is fine, just to reshape and remove any winter-damaged tips. Never hard-prune lavender in spring. That’s a reliable way to kill it. Spring pruning is for tidying only, not for the main annual cut.
How Hard to Cut
The rule of thumb: cut back to about 2cm above where the current year’s green growth meets the old woody stem.
In practice:
- Take off the spent flower stalks first (this alone tidies the plant a lot)
- Then cut the leafy green stems back by roughly two thirds of their length
- Keep shaping as you go, aim for a tight dome, slightly wider at the base than the top
- Stop well above the brown woody framework. If you’re getting close to old wood, leave more green rather than less.
A common beginner mistake is cutting “too gently” and only removing the flower stalks. That’s not enough, the plant needs a proper shaping cut to stay compact. Without it, the gaps in the dome get bigger every year and the whole plant legs up.
English Lavender vs French and Spanish Lavender
The pruning approach is slightly different depending on which lavender you’ve got.
English Lavender (Lavandula angustifolia)
- Fully hardy in the UK, survives cold winters outdoors
- Flowers in June and July
- Main prune: late August or early September
- Varieties: ‘Hidcote’ (deep purple, compact), ‘Munstead’ (mid-purple, hardy), ‘Royal Velvet’ (dark purple, good for cutting)
- Lives 8-10 years with correct pruning; 3-5 years without
French / Spanish / Italian Lavender (Lavandula stoechas)
- Not fully hardy, can suffer in cold Surrey winters
- Flowers earlier and for longer (May to September)
- Main prune: immediately after the main flush in July, then tidy any later flowering in September
- Distinctive “ears” at the top of each flower spike (actually modified bracts)
- Needs a sheltered spot; often grown in pots so it can be moved to shelter
Lavandula × intermedia (lavandin, Grosso, Provence) is a hybrid grown commercially for oil. If you’ve got one of these, prune after flowering in August, the same as English lavender.
If you’re not sure which you’ve got: look at the flowers. Short, fat flowers with papery “ears” on top = L. stoechas. Long, slim, tapering spikes = L. angustifolia or × intermedia.
Step-by-Step: The Annual Pruning Method
- Wait for the flowers to fade, don’t cut while they’re still looking good. Bees still want them. Late August is usually the right window in the south of England.
- Start with the spent flower stalks. Cut these off cleanly just above the foliage.
- Assess the shape. Step back and look at the plant as a whole, you’re aiming for a neat rounded dome.
- Cut back the green stems by about two thirds of their length. Work evenly around the plant.
- Keep the cut in the green. If you can see brown wood just below where you’re about to cut, stop and cut higher up.
- Don’t cut the centre too short. Slightly taller in the middle than the edges holds the dome shape.
- Clean up the prunings, they make excellent dried lavender. Hang upside down in bunches in a dry shed for two weeks.
A healthy, well-pruned lavender should look about 30% smaller after pruning than it did before. Anything less and you’re under-cutting.
What to Do With Old Leggy Lavender
This is the sad part of the article. If you’ve inherited a lavender from a previous owner and it’s now:
- A sprawling mess with bare brown stems in the middle
- Flowering only at the outer tips
- Hollow in the centre
- More than 5-6 years old and never correctly pruned
…it’s probably finished. Lavender cannot be “renovated” the way a neglected buddleia or hydrangea can. Cutting hard into the old wood to start again won’t work, the plant will simply die.
Your options:
- Accept and manage. Keep doing the light annual prune on whatever green growth remains. The plant will live another year or two but won’t recover its shape.
- Replace. Dig out, add fresh compost and grit to the soil, and plant new lavenders in late spring. A £6 young plant correctly pruned for 10 years is a better investment than trying to save an £80 specimen that’s already gone leggy.
- Take cuttings. If you want to keep the genetics, take semi-ripe cuttings in August from the healthy tips before you replace the parent plant.
It’s hard advice to give and harder to hear, but cutting an old lavender into the brown wood in hope is a guaranteed way to kill it. Better to replace and prune the new one right from year one.
Tools You’ll Need
- Sharp shears or secateurs, shears are quicker on a big plant; secateurs give a neater finish on a small one. Blunt blades crush the stems and invite disease.
- A bucket or sheet, to catch prunings. The dried flower stems are useful for sachets, moth repellent, and craft use.
- Gloves, lavender oils can irritate skin with prolonged contact, and stems scratch.
You don’t need loppers or a saw. If you’re reaching for either, you’re about to cut into old wood, which you shouldn’t be doing.
Common Lavender Pruning Mistakes
- Hard-pruning in spring. The single most common way lavenders are killed. Spring is for light tidying only.
- Cutting into the brown wood. No regrowth. The plant never recovers.
- Pruning too gently. Just removing the flower heads isn’t enough. The plant gets leggier every year.
- Pruning in winter. Cuts don’t heal in cold, wet weather. Dieback follows.
- Not pruning at all. A lavender left unpruned for 3-4 years is usually unsaveable by year five.
- Watering too much after pruning. Lavender is a dry-soil Mediterranean plant. Soggy feet kill it faster than a hard winter.
Frequently Asked Questions
Can I hard prune lavender?
No. Lavender does not regrow from old brown wood. A hard prune that cuts into the woody base will kill the plant. Every prune must stay within the current year’s soft green growth, cut back by about two thirds, but keep the cut above the brown framework.
Will lavender regrow from old wood?
No. This is the key thing that separates lavender from most other shrubs. Once a stem has turned brown and woody, it won’t produce new leaves or shoots. You cannot renovate a leggy old lavender by cutting it hard, the plant needs replacing.
When should you not prune lavender?
Never prune in winter (November to February), cuts don’t heal in the cold and damp, and dieback follows. Don’t hard-prune in spring; that’s a fast way to kill the plant. The only windows are a light tidy in March/April and the main annual cut in late August or early September.
What happens if I don’t prune lavender?
It gets leggy. Without an annual cut, the plant extends further and further from its base each year, the centre goes bare, and flowering drops off. Within 3-5 years an unpruned lavender is usually unsaveable. A correctly pruned plant lives and flowers well for 8-10 years.
Should I cut lavender back to the ground?
No. Cutting to the ground means cutting into old wood, and lavender doesn’t regrow from old wood. Leave at least 10-15cm of green, leafy growth above the woody base. The plant should look like a tight green dome after pruning, not a stump.
When is the best time to cut back lavender in the UK?
Late August or early September, immediately after flowering, while the weather is still warm enough for the plant to put on a small flush of new growth before winter. Cutting earlier wastes flowers; cutting later exposes fresh cuts to autumn damp and frost.
How do I know if my lavender is too old to save?
If the centre is bare brown wood and flowering only happens at the outer tips, and the plant is more than 5-6 years old, it’s probably beyond saving. Cutting hard into the old wood to renovate won’t work. Better to replace with a young plant and prune it correctly from year one.
Want Your Lavender (And Borders) Pruned Properly?
Lavender is one of those plants where the rules are simple but unforgiving, one bad prune can kill a mature plant. We handle lavender and perennial border maintenance as part of seasonal garden visits across Surrey and Sussex, including the August cut, at the right time, with sharp shears and the experience to know where to stop.
