Key takeaways
- Grow cumin under glass in the UK for a reliable seed crop
- Sow in March or April, one or two seeds per 15cm pot, 5mm deep
- Cumin hates root disturbance, so sow where it will grow
- Give it the sunniest, warmest spot and water sparingly
- Cut seed heads when they turn brown, dry them indoors, then rub out the seed
- Yields are small, so grow it for flavour and fun rather than to fill the spice jar
Yes, you can grow cumin in the UK, but it needs a greenhouse, polytunnel or sunny conservatory. Cumin is a small, feathery annual from hot, dry places. It needs a long warm summer to flower and ripen its seed, which the British outdoors rarely gives it.
The crop is small, but there’s something special about toasting cumin seed you grew yourself. This guide covers sowing, growing, harvesting and storing. If you want a whole curry-cabinet bed, our guide to growing Indian and Eastern spices in the UK covers turmeric, fenugreek and more.
Why does cumin need a greenhouse in the UK?
Cumin needs steady warmth to flower and set seed. A cool or wet British summer slows it right down. Outdoors it may grow leaves but give little ripe seed before autumn.
Under glass, summer days are much warmer, so plants flower and ripen in time. A south-facing greenhouse or polytunnel is ideal. A sunny conservatory works for a few pots. A cold frame is fine for young plants but too cramped and cool for ripening.
Cumin fits neatly alongside tomatoes, peppers, aubergines and basil, which like the same warm conditions. It’s a relative of coriander, which is far easier outdoors. The coriander growing guide explains how to keep that one from bolting.
Cumin flowering in midsummer. Its tiny white and pink flower heads look a lot like coriander, its close cousin.
How to sow cumin seed
Sow from March to April under glass. Earlier sowings give the longest growing season.
- Soak the seed in warm water for a few hours to soften the coat.
- Fill 15cm pots with peat-free seed or multipurpose compost mixed with a little grit or perlite.
- Sow two seeds per pot, 5mm deep, and cover lightly.
- Keep at about 20°C in a heated propagator or on a warm windowsill.
- Seedlings usually appear within one to two weeks.
- Keep the stronger seedling in each pot and snip off the other.
Cumin hates having its roots disturbed, so sow straight into its final pot rather than a seed tray. Don’t use garden soil, which can carry the fungi that cause damping off.
Young seedlings need a light, steady drink. Water the compost gently and let the top dry before the next one.
Growing cumin through the summer
Give cumin the sunniest, warmest spot in the greenhouse. Plants grow about 30-50cm tall with fine, thread-like leaves.
A ring of twine and a few canes stops slender cumin stems flopping once the seed heads form.
- Water sparingly. Let the top of the compost dry out between waterings. Wet roots lead to rot.
- Feed lightly. A weak liquid feed every couple of weeks once flowers form is plenty.
- Support stems. Thin stems can flop under seed heads. A short cane or a ring of twine helps.
- Keep it warm. Shut vents earlier in the evening on cool days to hold the heat in. Open them on hot days so plants don’t scorch.
The greenhouse ventilation guide has more on opening vents and shading through the year.
Pests and problems under glass
Cumin has few problems. These are the ones to watch.
- Aphids on shoot tips. Squash them or wipe them off with a damp cloth.
- Red spider mite in hot, dry greenhouses. Look for fine pale speckling and webbing, and see the spider mite guide. Damp down the floor on hot days. A biological control, Phytoseiulus persimilis, works well.
- Powdery mildew in still, damp spells. Improve airflow and remove affected leaves.
- Damping off in seedlings. Use clean pots and fresh compost, and don’t overwater.
How to harvest and dry cumin seed
Cumin seed is ready when the seed heads turn brown and the seeds come away easily. In the UK this is usually from late summer into early autumn.
Cut cumin seed heads once they turn brown and dry. The ridged seeds are easy to rub out once they’ve dried indoors.
- Cut the whole seed heads with a short stalk on a dry day.
- Put them head-down in a paper bag, or spread them on a tray.
- Leave somewhere warm and airy indoors for one to two weeks.
- Rub the heads between your hands over a bowl to free the seed.
- Gently blow away the chaff, or pour the seed between two bowls outside on a breezy day.
- Store the clean, dry seed in an airtight jar in a dark cupboard.
Whole seed keeps its flavour much longer than ground. Grind only what you need. Our guide to drying and storing herbs has more tips for keeping homegrown flavour.
Toast whole cumin seed in a dry pan for a minute or so, just until it smells fragrant, then grind it.
Can you save your own cumin seed?
Yes. Keep back a few of the biggest, best-ripened seed heads for sowing next spring. Store the seed somewhere cool, dry and dark. Germination falls as seed ages, so sow fresh seed every year or two.
Whole cumin from a grocer can sometimes sprout if it hasn’t been heat-treated. It’s a gamble, so sow a few extra.
Cumin growing calendar
| Month | What to do |
|---|---|
| February | Buy seed and clean pots |
| March | Sow under glass in a heated propagator |
| April | Last sowings. Thin to one seedling per pot |
| May | Move pots to the sunniest greenhouse spot |
| June | Water sparingly. Stake if stems flop |
| July | Flowering. Light feeds every couple of weeks |
| August | Seed heads swell and start to colour |
| September | Cut brown seed heads and dry indoors |
| October | Rub out, clean and store seed |
Common mistakes when growing cumin
Growing it outside. In most British summers outdoor plants give little ripe seed. Keep cumin under glass.
Sowing too late. May or June sowings may not ripen before autumn. Sow in March or April.
Transplanting seedlings. Cumin sulks or bolts when its roots are disturbed. Sow straight into the final pot.
Overwatering. Soggy compost causes rot. Let it dry a little between drinks.
Expecting a big harvest. Each plant gives only a pinch. Grow plenty of pots if you cook with it often.
Frequently asked questions
Can cumin grow in the UK?
Yes, but it needs a greenhouse, polytunnel or conservatory for a reliable crop. Cumin needs a long, hot summer to flower and ripen its seed. Outdoors in the UK it often grows leaves but little ripe seed.
When should I sow cumin in the UK?
Sow cumin in March or April under glass. Sow straight into 15cm pots, 5mm deep, and keep them at about 20°C. Later sowings may not ripen seed before autumn turns cool.
How long does cumin take to grow?
Cumin takes roughly three to four months from sowing to ripe seed. Spring sowings under glass usually flower in summer and ripen from late summer into early autumn.
How much cumin does one plant give?
One plant gives only a small pinch of seed. Grow a dozen or more pots if you want enough for regular cooking. Many people grow it for the fun and the fresh flavour rather than the quantity.
Can I grow cumin from supermarket seeds?
Sometimes, if the whole seed hasn’t been heat-treated. Germination is unpredictable, so sow several per pot. Seed from a seed company is more reliable.
Is home-grown cumin worth it?
It’s worth it for flavour and curiosity, not to save money. Freshly dried seed tastes bright and aromatic. Yields are small, so think of it as a special treat for the spice rack.
For more spice and herb ideas, browse the growing hub. Then try something easier outdoors with our guide to growing herbs in the UK.
Our team produces practical UK gardening guidance from source research, contributor records and established horticultural practice. Editorial standards are overseen by Matt W.
