A well-established rosemary plant can provide more than herbs for Sunday dinner. Its younger shoots are useful material for making new plants, allowing you to replace an ageing woody shrub or fill another sunny container without buying a new specimen.
Growing rosemary from seed is possible, but slow. Taking cuttings from a healthy existing plant is normally more practical, and the new plants should resemble the parent cultivar. The key is to select the right stem, prepare it cleanly and keep the rooting medium moist enough without allowing the base to rot.
Choose the right season
The Royal Horticultural Society recommends softwood cuttings from new growth in late spring or summer, and semi-ripe cuttings later in summer. Those are two stages of the current season's shoots.
Softwood is green, flexible young growth. Semi-ripe material has started firming towards the base but still has a softer tip. Very old, thick, woody stems are less convenient to root.
In Britain, taking cuttings during an active growth period gives them useful warmth and light. An autumn cutting may survive in protected conditions, but it has less time to establish before winter.
Take cuttings from a healthy parent
Look for shoots with good green foliage and no signs of pests or disease. A non-flowering shoot is preferable because it can concentrate on rooting instead of maintaining flowers.
Avoid stems that are brown, brittle or damaged by winter wet. If the parent itself is dying from root rot, taking a cutting from a sound tip might be worthwhile, but inspect it carefully and discard diseased tissue.
Collect material in the morning when stems are well hydrated. Use clean sharp secateurs and place the pieces in a clean bag if you cannot prepare them immediately. Don't leave delicate shoots wilting on a sunny bench for hours.
Cut each stem to a manageable length
Take several shoot tips, roughly 8–12cm long for a straightforward home propagation attempt. Different rooting methods may recommend slightly different lengths, so don't worry about making every cutting identical.
Trim the base just below a node, the point where leaves join the stem. Remove leaves from the lower portion that will sit below the compost surface. Keep a useful tuft of foliage at the top.
Make a clean cut rather than crushing the base. If a stem carries a flower bud, remove it. Avoid stripping every leaf because the cutting still needs its upper foliage while new roots are forming.
Prepare a free-draining rooting medium
A small pot or seed tray with drainage holes is enough. Fill it with a suitable peat-free propagation compost, often improved with horticultural grit or another material that keeps the medium open.
Water lightly and allow excess moisture to drain. A saturated, airless compost can cause cuttings to blacken before they form roots. Rosemary is a Mediterranean shrub and does not benefit from sitting in a permanently wet pot.
Use a pencil or dibber to make holes. Inserting a cutting into a prepared hole avoids scraping off tissue and makes it easier to firm the compost around the stem.
Insert the cuttings
Put the bare lower portion of each cutting into the hole, leaving the leafy tip above the surface. Firm the compost gently so the stem stands upright.
Space cuttings so the leaves aren't all pressed together. You can put several into one small tray, but overcrowding increases the risk of stale humid air and makes it harder to notice a rotting stem.
Label the pot with 'rosemary', the variety if known, and the date. A label becomes particularly useful if you're propagating several herbs with similar narrow leaves.
Provide warmth, light and humidity
Place the cuttings in bright, indirect light, away from scorching midday sunshine. A clear ventilated propagation cover can help prevent the foliage losing too much moisture while the cuttings lack roots.
Check for condensation and improve airflow if the cover stays dripping wet. A suitable room temperature is often enough during summer. Warmth helps, but placing the pot on a radiator can dry or overheat it.
Keep the compost lightly moist rather than soaked. Resist the temptation to water automatically every day; check the medium first.
Rooting hormone: useful but not essential
Some gardeners dip prepared cuttings into an appropriate rooting gel or powder. This can help with certain species or more difficult material, but rosemary commonly roots from correctly prepared cuttings without specialist products.
If you use a rooting preparation, follow its label and pour a small amount into a separate container rather than contaminating the original pot.
Don't use extra fertiliser as a substitute for rooting conditions. A cutting with no roots cannot make full use of feed and may be damaged by overly concentrated nutrients.
How long before roots appear?
There is no guaranteed number of days. Warmth, moisture, shoot maturity and the health of the parent plant all influence success.
Look for fresh growth at the tip and a firmer hold in the compost over time. A very gentle test may indicate rooting, but repeatedly tugging a cutting upward can break its new roots.
If one cutting turns black, remove it promptly to prevent decaying material sitting among healthy pieces. Others may take longer and still establish.
Pot up only when the roots are ready
When a cutting has a sound little root system, transfer it into its own small pot of suitable free-draining peat-free compost. Handle the young roots gently.
Do not put a tiny rooted rosemary into a huge deep planter. Excess damp compost may remain wet for too long. Choose a pot that accommodates the roots with a modest amount of growing room.
Water enough to settle the compost and let it drain. Keep the new plant sheltered while it adapts, then gradually move it towards a sunnier position.
Can you root rosemary in water?
Some rosemary stems will produce roots in water, but results can be inconsistent. A clean jar, a submerged lower node and leaves kept above the water are the basics if you want to experiment.
Replace cloudy water and keep the jar in bright indirect light. If roots develop, move the cutting into an airy potting mix carefully rather than leaving it indefinitely in stagnant water.
For several reliable plants, compost propagation is generally a sound method and avoids the additional transition from water-grown roots to soil.
Care for your young rosemary
Rosemary needs a sunny position and good drainage once established. Keep a small newly rooted plant watered during dry spells, but do not treat it like moisture-loving mint.
If cuttings were taken late in the season, protect them from prolonged frost and winter wet while their root systems are small. Move them into the garden once conditions are suitably warm and they have enough roots to cope.
Take several cuttings rather than relying on one. That gives you room for an occasional failure without damaging the original shrub through repeated large harvests.
Troubleshooting propagation problems
Blackened bases suggest rot associated with excess moisture, damaged cuttings or poor ventilation. Recheck drainage and take fresh healthy cuttings if necessary.
Drooping tips may have lost water faster than they can replace it. Reduce harsh light, improve humidity carefully and prepare fresh material quickly after cutting.
Cuttings that remain green but refuse to grow may simply be slow. Give them suitable warmth and patience rather than pulling them up every week or applying stronger fertiliser.
Healthy rosemary cuttings are an economical way to keep a favourite variety going. The method depends on selecting suitable young shoots and maintaining balanced conditions while roots develop.