How to Propagate Medicinal Herbs in Late Summer in the UK

Late summer is a season of abundance in the herb garden. Your plants are leafy, established and full of life — but the first cooler nights are already hinting that autumn is on its way.

This makes August and early September an excellent time to propagate many medicinal and traditional healing herbs in the UK. With a few healthy parent plants, you can create new stock for next year, replace older specimens and preserve favourite varieties before winter arrives.

You do not need a greenhouse or specialist equipment. A clean pair of secateurs, a few small pots and a sheltered place out of harsh sun are enough to begin.

Why Propagate Medicinal Herbs in Late Summer?

By late summer, established herbs have produced plenty of healthy growth. Non-flowering shoots can be used for cuttings, mature clumps can be divided and seeds can be gathered from plants that have completed flowering.

Propagating now can help you:

• Create more plants without buying mature specimens

• Replace short-lived or woody herbs

• Preserve a particularly vigorous, aromatic or attractive plant

• Build up enough stock for hedges, containers and dedicated herb beds

• Produce spare plants to share with friends and family

• Keep tender herbs under protection over winter

Timing matters. New plants need enough warmth and daylight to establish roots before temperatures fall sharply, so it is best to begin during August or, in milder areas, early September.

Three Ways to Propagate Herbs in Late Summer

The most useful methods at this time of year are cuttings, division and seed collection. The right method depends on the herb and its stage of growth.

How to Take Late-Summer Herb Cuttings

Cuttings allow you to produce a new plant that is genetically identical to the parent. They are especially useful for named varieties, plants with exceptional aroma and herbs that do not come true from seed.

In late summer, the ideal shoots are often semi-ripe: still flexible at the tip but beginning to firm at the base.

Herbs Suitable for Late-Summer Cuttings

• Rosemary

• Common sage and culinary sage varieties

• Lavender

• Thyme

• Hyssop

• Lemon verbena

• Scented pelargonium

• Southernwood

What You Will Need

• Clean, sharp secateurs or a propagation knife

• Small pots with drainage holes

• Peat-free seed or cuttings compost

• Horticultural grit or perlite

• Plant labels and a pencil

• A clear propagator lid or loose plastic bag, if required

Step-by-Step Method

1. Choose a healthy parent plant. Select vigorous growth without discolouration, pests or disease. Water the plant the evening before if the soil is dry.

2. Cut in the morning. Take shoots when they are well hydrated and the day is still cool. Choose non-flowering stems around 7–10cm long.

3. Prepare each cutting. Make a clean cut just below a leaf joint. Remove the leaves from the lower third to half of the stem, along with any flowers or buds.

4. Prepare the pot. Mix peat-free cuttings compost with grit or perlite to create a free-draining medium. Water it lightly and allow excess moisture to drain.

5. Insert the cutting. Make a hole with a pencil or dibber and place the bare part of the stem into the compost. Firm gently. Several cuttings can be placed around the edge of one pot, provided their leaves do not overlap heavily.

6. Provide gentle humidity. Cover moisture-loving cuttings loosely with a clear bag or propagator lid. Keep the covering away from the foliage and open it regularly for ventilation. Grey-leaved Mediterranean herbs such as lavender and sage dislike stale, overly humid conditions and need particularly good airflow.

7. Place somewhere sheltered. Keep the pot in bright, indirect light, away from strong afternoon sun and cold winds. An unheated greenhouse, cold frame, porch or bright windowsill may be suitable.

8. Check for rooting. Keep the compost lightly moist, never saturated. After several weeks, gentle resistance when you lightly tug the stem usually indicates that roots have formed.

Once rooted, pot each cutting separately and allow it to become established before winter.

How to Divide Established Medicinal Herbs

Division is often the quickest way to multiply clump-forming perennial herbs. It also rejuvenates crowded plants whose centres have become weak or congested.

Late-summer division works best when the soil is moist, the worst heat has passed and there is still time for new roots to settle. In hot, dry weather or colder northern gardens, it may be better to wait until early spring.

Herbs That Can Be Divided

• Lemon balm

• Peppermint and other mints

• Feverfew

• Chives

• Valerian

• Yarrow

• Meadowsweet, where growing conditions are suitably moist

Step-by-Step Method

1. Water the plant thoroughly the day before lifting it.

2. Cut back excessively tall or tired top growth to reduce moisture loss.

3. Lift the clump carefully with a garden fork, keeping as much root intact as possible.

4. Pull the plant apart by hand or divide it with two forks or a clean spade.

5. Discard any dead, woody or diseased material from the centre.

6. Replant healthy outer sections at the same depth they were growing previously.

7. Water deeply and keep the soil consistently moist while the divisions establish.

Mint and lemon balm can spread vigorously. Growing new divisions in containers is a simple way to keep their roots under control.

Collecting and Sowing Herb Seeds

Late summer is also the season for seed saving. Allow flower heads to mature on the plant until the seeds are dry and beginning to loosen, then collect them on a dry day.

Place each seed head into a labelled paper bag and leave it somewhere airy for a few days. Rub or shake out the seeds, remove as much chaff as practical and store them in labelled paper packets inside a cool, dry, dark container.

Herbs to Collect Seed From

• Calendula

• German chamomile

• Borage

• Feverfew

• Motherwort

• Holy basil

• Echinacea

Some hardy herbs can be sown fresh in late summer or autumn. Others are best stored for spring. Echinacea and certain other perennial herbs may germinate more reliably after a period of cold, moist conditions, known as stratification.

Seed-grown plants are not always identical to their parent, especially where several varieties have flowered nearby and cross-pollination is possible. Use cuttings or division when you want to preserve the exact characteristics of a favourite plant.

Best Medicinal Herbs to Propagate in Late Summer

Rosemary

Take non-flowering semi-ripe cuttings from healthy shoots. Use a very free-draining compost and avoid excessive humidity. Young plants benefit from protection against prolonged frost and winter wet.

Sage

Sage can become woody and less productive with age, so regular propagation is worthwhile. Take sturdy, non-flowering shoots and provide excellent drainage and airflow.

Lavender

Choose short side shoots without flowers. Semi-ripe cuttings taken in late summer can root well, but they must not sit in wet compost. Keep young plants sheltered from persistent winter rain.

Lemon Balm

Lemon balm is easy to multiply by division. Replant healthy pieces promptly and water them well. It can also self-seed freely, so remove unwanted seedlings before they spread.

Peppermint

Divide rooted runners or sections from the edge of an established clump. Container growing is usually advisable because peppermint spreads rapidly through underground stems.

Feverfew

Feverfew can be divided, moved as a young self-sown seedling or raised from collected seed. Water transplants carefully until they recover.

Lemon Verbena

Take cuttings before nights become cold. Lemon verbena is tender in much of the UK, so rooted plants are best overwintered somewhere frost-free with reduced watering.

Caring for Newly Propagated Herbs

Young plants are more vulnerable than established ones. The aim is to encourage steady root development without forcing soft, lush growth as autumn approaches.

Light: Give cuttings bright, indirect light. Move rooted plants gradually into brighter conditions rather than exposing them suddenly to strong sun.

Watering: Keep the compost lightly moist while roots develop. Waterlogging is one of the most common causes of failure, particularly with rosemary, sage, thyme and lavender.

Feeding: Cuttings do not usually need feeding before they root. Once established, a very weak liquid feed may be used if growth is pale, but avoid encouraging tender growth late in the season.

Ventilation: Provide airflow around leaves and remove any fallen or mouldy material promptly.

Potting on: Move rooted cuttings into individual pots while the weather is still mild. Handle the young roots gently.

Labelling: Record the herb, variety, propagation method and date. Small plants can look surprisingly similar during winter.

How to Overwinter Young Herb Plants in the UK

The best winter position depends on the herb and your local climate.

Hardy plants such as mint, lemon balm and feverfew can often remain outside once well rooted, although small pots should be sheltered from severe frost and waterlogging. Place them against a wall, group pots together or move them into an unheated cold frame.

Mediterranean herbs such as rosemary, sage and lavender usually tolerate cold better than wet roots. Keep containers raised on pot feet and protected from prolonged winter rain.

Tender plants, including lemon verbena and scented pelargoniums, should be moved to a bright, frost-free place before the first frost. Water sparingly during winter but do not allow young roots to dry out completely.

In exposed, northern or high-altitude gardens, give all newly propagated plants more protection than established specimens.

Common Propagation Mistakes to Avoid

• Taking cuttings from flowering, weak or diseased shoots

• Using blunt or unclean tools

• Choosing pots without adequate drainage

• Keeping Mediterranean herbs too wet or humid

• Placing fresh cuttings in strong direct sunlight

• Dividing plants during very hot, dry weather

• Leaving tender herbs outside until after the first frost

• Forgetting to label plants and seed packets

• Potting on before sufficient roots have formed

Frequently Asked Questions

Is August too late to take herb cuttings in the UK?

No. August is often one of the best months for semi-ripe cuttings because the shoots have begun to firm while temperatures are still warm enough for rooting. Start promptly so the new plants have time to establish before winter.

Can I propagate rosemary in September?

You can take rosemary cuttings in early September, particularly in a mild area or if you can offer sheltered protection. Rooting may take longer as temperatures and light levels fall.

Do herb cuttings need rooting powder?

Many common herbs root successfully without it. Rooting powder may help some slow or woody material, but fresh, healthy cuttings, clean tools and suitable compost are more important.

Can I root herb cuttings in water?

Soft-stemmed herbs such as mint and lemon balm often root in water. Woody Mediterranean herbs are generally more reliable when rooted in a free-draining compost, where the new roots are better adapted to potting conditions.

Should I keep herb cuttings indoors over winter?

Tender herbs need frost-free protection. Hardy herbs may remain in a cold frame, unheated greenhouse or sheltered outdoor position once rooted. Avoid keeping hardy plants in a very warm room, where low winter light can cause weak growth.

When can I plant propagated herbs into the garden?

Well-established hardy plants may be planted in mild autumn conditions, but small or recently rooted plants are usually safer kept protected and planted out in spring after the worst weather has passed.

Grow Next Year’s Herb Garden for Free

Late-summer propagation turns the final flush of the growing season into the beginning of next year’s garden. A few carefully chosen cuttings, divisions and saved seeds can become productive plants for beds, pots and wildlife-friendly borders.

Begin with the healthiest herbs you already grow, label everything clearly and give young plants a little extra protection through their first winter. By spring, you may have an entirely new generation ready to plant, share and enjoy.

The herbs discussed in this article have histories of traditional use. This guide is about growing and propagation and is not medical advice. Always identify plants correctly and seek appropriate professional advice before using any herb medicinally, particularly during pregnancy, while breastfeeding, when taking medication or when managing a health condition.

Learn More

• Link rosemary, sage, lavender, lemon balm, peppermint, feverfew, lemon verbena and echinacea to relevant plant or seed product pages.

• Link how to dry herbs to: The Complete Beginner’s Guide to Drying Every Type of Healing Herb.

• Link starting a medicinal herb garden to a suitable beginner’s guide or collection page.

Ready to grow your own healing herb garden? Explore our collection of medicinal and culinary herb plants, carefully selected for UK gardens.