Rosemary looks tougher than it is when the secateurs come out. An established plant can tolerate regular light trimming, but a hard cut into thick, bare stems may leave branches that never grow back. The most dependable approach is to shorten the green leafy shoots after flowering, while keeping the old woody framework intact.
The Royal Horticultural Society advises trimming rosemary annually after the flowers fade. That keeps the plant compact and encourages fresh growth. If a shrub is already very woody and bare, growing a replacement from cuttings is often more reliable than trying to force it into a new shape.
Look at the plant before cutting
Culinary rosemary is now botanically named Salvia rosmarinus, although you may still see the older name Rosmarinus officinalis on labels. It is an evergreen Mediterranean shrub that enjoys sunshine and well-drained soil.
Follow a branch from the tip towards the centre. The younger growth normally carries plenty of narrow, fragrant green leaves. Deeper down, the branch becomes hard, brown and sometimes almost leafless.
That change matters. The soft leafy portion is usually a safe place for a light trim. Thick bare wood is far less dependable for producing replacement shoots.
Different cultivars may be upright, arching or trailing. Keep that natural shape in mind rather than cutting every plant into the same round ball.
When to prune rosemary in the UK
The RHS recommends a light trim after flowering. For many plants, that falls in late spring or early summer, although the timing varies with variety, weather and growing conditions.
Look at the flowers on the actual shrub instead of relying on a date from another gardener's calendar. Once most blooms have faded, you can shorten long young shoots and remove the flowered tips.
Avoid severe autumn pruning. Fresh shoots encouraged just before cold weather may have little time to mature. If an isolated branch is dead or damaged, you can remove it when necessary, but ordinary shaping is best done while the plant has a growing season ahead.
In an exposed northern garden, wait until there is clear active growth before attempting a stronger tidy-up. A mature rosemary on a sheltered south-facing wall may start growing earlier.
The safest method for a healthy shrub
Use sharp, clean secateurs. Begin with obvious dead, damaged or badly crossing shoots. Work carefully so you don't remove useful main branches by mistake.
Next, shorten the longest green leafy tips. Make a clean cut just above a point where living leaves or side growth remain. Step back every few cuts and look at the overall outline.
Keep plenty of foliage on each branch. The goal is to tidy the plant and encourage new shoots, not strip it down to sticks. Where one branch is far longer than the others, shorten it in stages rather than making a drastic cut below its last leaves.
An upright rosemary can be maintained as a low hedge by trimming leafy growth lightly each year. A trailing rosemary is better allowed to cascade naturally, with only excessively long or damaged stems shortened.
Why cutting into old brown stems is risky
Rosemary doesn't reliably regenerate from bare old wood. The RHS specifically warns against heavy pruning into older stems and recommends replacing very woody, straggly plants.
A long brown branch with only a tuft of leaves at the end may be tempting to cut back to the centre. But if no living buds remain below your cut, you can be left with a dead-looking gap.
Don't follow advice telling you to cut every rosemary plant down by half without checking where its healthy growth begins. More severe renovation guidance applies to particular conditions and isn't a promise that any exhausted old bush will recover.
If the plant is extremely overgrown, take cuttings from healthy growth while you still have it. You can then renew the planting without risking the entire old specimen at once.
Pruning rosemary in a container
Potted rosemary is easy to move near the kitchen, but its roots have less access to moisture than those of a shrub in the ground. A small container in full summer sun can dry out quickly.
Check the compost before pruning. A plant suffering from prolonged drought, waterlogging or an exhausted root system may not respond well to even a moderate haircut.
Keep the pot somewhere bright, with free drainage and suitable gritty compost. Don't allow it to sit in a decorative cover full of water. In cold weather, protect the root ball of a container plant where freezing is a risk.
After a light spring or summer trim, continue ordinary care and avoid heavy feeding. Rosemary usually manages well without rich soil, especially when grown in the ground.
What if your rosemary has become leggy?
A leggy rosemary may have long stems with foliage only near the tips. Poor light, age and lack of regular trimming can all contribute.
Check the position first. A plant crowded by taller shrubs may stretch towards sunlight. Improving the conditions helps future growth, though it won't instantly cover old bare wood with new leaves.
Shorten the remaining leafy tips gently if the plant is vigorous. If the middle is almost entirely bare, the sensible solution may be replacement. The RHS notes that rosemary can become straggly as it ages even with normal care.
Rather than buying a large new shrub, try rooting cuttings from a healthy plant in late spring or summer. That also preserves a variety whose flavour or growing habit you already like.
Can you take rosemary cuttings while pruning?
Yes, when the pruned shoots are healthy and at a suitable stage. The RHS recommends softwood cuttings from fresh growth in late spring or summer, and semi-ripe cuttings in summer.
Select a non-flowering shoot where practical. Remove leaves from the lower part, then plant the stem in a free-draining propagation mix according to a reliable cuttings method.
Avoid taking all your cuttings from an exhausted, diseased shrub. A healthy young shoot has a better chance of rooting, and the parent plant still needs enough foliage to support itself.
Label the cuttings and keep them in suitable light while roots form. Once they are well established, you can pot them on or use them to replace an old rosemary hedge.
Harvesting rosemary for cooking
Regular small harvests of leafy tips can help keep a culinary rosemary bush compact. Use clean snips rather than pulling shoots away from the stems.
Rosemary is evergreen, so healthy sprigs are available through much of the year. The softer new growth of late spring and summer is often especially pleasant to use in cooking.
Spread harvests across the shrub instead of repeatedly stripping one side. Remove only what you need during winter, when replacement growth is slower.
To dry extra sprigs, hang them in a warm, dark, ventilated place. When fully dry, strip the leaves and store them in a clean airtight jar.