How to propagate culinary herbs: when to sow from seed, how to take softwood and semi-ripe cuttings, and how to divide and layer perennials to make new plants.
The short answer¶
Most annual herbs are grown from seed. Woody herbs — rosemary, thyme, sage, lavender, hyssop — are best from cuttings, which are quick and give plants identical to the parent. Clump-forming perennials such as chives, mint, oregano and sorrel are easiest of all: dig them up and divide them. A few herbs, notably French tarragon, set little or no viable seed and can only be propagated vegetatively; seed sold as "tarragon" is almost always the coarser Russian kind.
From seed¶
| Herb | Germination temperature | Time to germinate | Tips |
|---|---|---|---|
| basil | 18–24 °C | 5–10 days | Surface-sow thinly; do not overwater seedlings |
| parsley | 15–21 °C | 2–6 weeks | Notoriously slow; soaking seed overnight helps |
| Coriander | 15–20 °C | 1–3 weeks | Lightly crush the round "seeds" (each is two seeds in a husk) |
| dill, chervil | 10–20 °C | 1–3 weeks | Sow where they are to grow |
| chives | 15–20 °C | 1–2 weeks | Sow in clumps of several seeds |
| thyme, oregano | 15–21 °C | 1–3 weeks | Tiny seed; press onto the surface, do not cover deeply |
| sage | 15–21 °C | 1–3 weeks | Grows readily from seed |
| rosemary | 15–21 °C | Erratic, up to 3–4 weeks | Poor germination; cuttings are much easier |
| lovage, sorrel | 10–18 °C | 2–3 weeks | Easy; a single plant is often enough |
Sow into a fine, peat-free seed compost, cover lightly (roughly the seed's own depth; leave very fine seed uncovered), water from below and keep the compost moist but not wet. Once seedlings have their first true leaves, prick them out into individual cells or small pots. Damping off — seedlings collapsing at soil level — is caused by fungi thriving in cold, wet, stagnant conditions. Use clean pots, fresh compost and mains water for seedlings, and give them air.
Many herbs will self-seed if left to flower: borage, dill, chervil, lemon balm, fennel and parsley among them. It is the lowest-effort propagation there is, if not the tidiest.
Softwood and semi-ripe cuttings¶
Cuttings are sections of stem that are persuaded to grow roots. Softwood cuttings are taken from soft new growth in spring and early summer; they root fast but wilt easily. Semi-ripe cuttings are taken in mid to late summer from the current year's growth, which is firm at the base but still flexible at the tip; they are more robust.
💡 How to take a herb cutting
- Early in the morning, when the plant is full of water, cut a non-flowering shoot 7–10 cm long.
- Trim it just below a leaf joint (node) with a sharp, clean knife.
- Strip the leaves from the lower half. Pinch out the soft tip if it is long.
- Push the stem into a small pot of gritty compost (half multipurpose, half perlite or grit), around the edge of the pot. Several cuttings can share one pot.
- Water, then cover with a clear plastic bag or place in a propagator. Keep in bright light but out of direct sun.
- Roots usually form in three to eight weeks. Gentle resistance when you tug the stem, or roots at the drainage holes, means it has taken. Pot on individually.
Hormone rooting powder or gel is optional; most herbs root without it. Ventilate the bag every few days to prevent mould.
| Herb | Cutting type | When |
|---|---|---|
| rosemary | Semi-ripe (softwood also works) | June–September |
| thyme | Softwood or semi-ripe | May–August |
| sage | Softwood or semi-ripe | May–August |
| lavender | Semi-ripe, ideally a side-shoot with a "heel" | July–September |
| Bay | Semi-ripe | Late summer; slow, can take months |
| lemon verbena | Softwood | Late spring |
| mint, vietnamese coriander | Softwood | Spring to summer; will root in a glass of water |
| basil | Softwood | Summer; roots in water within a week or two |
Division¶
Division is simply cutting a clump into pieces, each with roots and shoots. Do it in early spring as growth begins, or in early autumn.
- Lift the clump with a fork.
- Pull it apart by hand, or cut it into sections with a spade or old bread knife. Tough clumps can be prised apart with two forks back to back.
- Discard the old, woody centre and replant the vigorous outer pieces at the same depth.
- Water well.
Herbs to divide: chives (every two to three years), mint (every year if in a pot), oregano, marjoram, sorrel, lovage, lemon balm, French tarragon (every three years or so, which also keeps it vigorous) and lemongrass. Supermarket pot herbs can also be divided — see growing herbs indoors.
Layering¶
Layering roots a stem while it is still attached to the parent. It suits sprawling woody herbs such as thyme, sage and rosemary, and is almost foolproof. In spring, bend a low stem down to the soil, scrape a little bark from the underside where it touches the ground, pin it down with a wire hoop or stone and cover that section with gritty compost. By late summer or autumn it should have rooted; cut it from the parent and move it. Some thymes and mints layer themselves naturally.
Runners and rhizomes¶
mint spreads by runners that root as they go; a 10 cm length of runner with a few buds, laid horizontally in a pot of compost, will make a new plant. horseradish, ginger and turmeric are grown from pieces of root or rhizome — see growing your own spices.
Common mistakes¶
- Taking cuttings from flowering stems. They root poorly; choose non-flowering shoots.
- Keeping cuttings too wet. Waterlogged compost rots stems before they root.
- Sowing parsley and giving up after a fortnight. Give it six weeks.
- Buying "tarragon seed" and expecting French tarragon.