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How to sow vegetable seeds in the UK

Updated: October 2026

The packet is in your hand, and one tray on one date will not suit every crop. This page is how to sow vegetable seeds in the UK: compost, depth, pricking out and frost. What the sleeve must say is on the [vegetable seed buying guide](/hub/herb-seeds/vegetable-seeds/sub/vegetable-seeds-buying-guide). Which packet fits which crop is on [best vegetable seeds](/hub/herb-seeds/vegetable-seeds/sub/vegetable-seeds-best). October strategy is on [vegetables to sow in autumn](/hub/herb-seeds/vegetable-seeds/sub/vegetable-seeds-autumn-sowing). The line-up is the [vegetable seeds comparison](/hub/herb-seeds/vegetable-seeds). The Products Compared editorial team updated this page on 15 October 2026 from RHS guidance, Which? tomato timing and Mr Fothergill's cauliflower page. No sowing trial. A qualifying purchase through our links can earn a commission at no extra cost to you.

The packet is in your hand, and one tray on one date will not suit every crop. This page is how to sow vegetable seeds in the UK: compost, depth, pricking out and frost.

Our top picks

Mr Fothergill's Mr Fothergill's Broad Bean Aguadulce

Best overall

Mr Fothergill's Mr Fothergill's Broad Bean Aguadulce
7.3/10about £3.49
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Mr Fothergill's Mr Fothergill's Cauliflower All The Year Round

Rank 2

Mr Fothergill's Mr Fothergill's Cauliflower All The Year Round
9.2/10about £2.09
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Just Seed Just Seed Lettuce Winter Density

Best value

Just Seed Just Seed Lettuce Winter Density
7.6/10about £3.10
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On this page
  1. 1.Tray, module or the row
  2. 2.Peat-free seed compost and water
  3. 3.Depth for the crops in this set
  4. 4.Tomatoes, light and frost
  5. 5.If the tray stays empty

Tray, module or the row

Small seed starts in a tray or in modules. A broad bean starts one to a pot, or in the row when the month and the site allow it. The RHS indoor method for cauliflower, lettuce and tomatoes is peat-free seed compost, firmed to about 1 cm below the rim, sown thinly, and covered no deeper than the seed unless the packet says otherwise. A broad bean goes 5 cm deep and germinates in cool compost. Sowing under cover from February keeps bean seed away from mice. The Generic Black Cherry reviews include a bag with no instructions, so the tomato method below comes from Which? and the RHS.

Peat-free seed compost and water

Use a peat-free seed compost for the small seed. It is finer than a multipurpose mix, and the RHS notes that the surface often looks dry while the compost underneath is still wet. Feel a centimetre down before you water again. Overwatering is the usual way a tray of cauliflower or lettuce collapses. Water with a fine rose, or from below, until the surface darkens, then stop. Take any lid off once you see green. Careful watering will not save seed that arrived already in its expiry month, which one Winter Density reviewer reported.
Mr Fothergill's Mr Fothergill's Broad Bean Aguadulce

Testsieger

Mr Fothergill's Mr Fothergill's Broad Bean Aguadulce
7.3/10about £3.49
View offer

Depth for the crops in this set

Broad beans go 5 cm deep, scar down, in a pot or in a row that will not sit waterlogged. Cauliflower All The Year Round, on Mr Fothergill's page, is 0.5 cm indoors and 1.5 cm outdoors. Indoor months on that page are January to March. Outdoor months are March to June, or September to October. The 60 cm on the same page is the gap when you plant out, not the gap between seeds in the tray. Sow lettuce thinly, and move it once it has a true leaf. Covering lettuce as deep as a bean leaves the tray empty. Covering a bean as shallow as lettuce leaves the seed where mice can find it.

Tomatoes, light and frost

Sow tomatoes for a greenhouse from about mid-March, and outdoor plants from early April, at 15–20°C. A February sowing on a dull UK windowsill grows a long weak stem before the last frost has gone. Plant outdoors only once frost is past, which Which? puts at mid to late May. The RHS wants nights above 7°C before any tender plant goes out, and tomatoes do better when nights stay above 10°C. Keep the bean pot out of a propagator set for tomatoes.

If the tray stays empty

RHS sowing guidance is that you often recover a failed sowing by sowing again within two weeks, while the season still allows it. Check the moisture under the surface, and the date, before you blame the seed. Two empty trays of the same packet are the moment to contact the seller with the count and the date.

Common questions

Do I sow everything in a tray?
Sow cauliflower, lettuce and tomatoes in a tray or in modules, in peat-free seed compost firmed to about 1 cm below the rim. Sow broad beans one to a pot, 5 cm deep, or in the row when the site and the month allow. A shallow tray is the wrong tool for a bean, and a 5 cm hole is the wrong depth for lettuce.
What compost, and how wet?
Use peat-free seed compost for the small seed. The surface often looks dry while the mix below is still damp, so feel underneath before you water. Overwatering is the common failure in these composts. Take the lid off once you see green. A bean pot does not need the 18°C the general indoor guide gives for most other seed.
How deep are beans, cauliflower and lettuce?
Beans go 5 cm deep, scar down if you follow the RHS. Cauliflower All The Year Round goes 0.5 cm indoors or 1.5 cm outdoors, on Mr Fothergill's page. Sow lettuce thinly, as the packet shows. The 60 cm cauliflower figure is the later planting distance. Winter Density's 1.5 cm and its September window are on the autumn page.
When do I prick out, and where do I hold the seedling?
Prick out once the seedling has a leaf you can hold, which is the RHS indoor method. Hold a leaf, not the stem, because a bruised stem is the plant you lose. Move cauliflower and lettuce on before they crowd. Only then apply the 60 cm the cauliflower will need in the bed.
When do tomatoes go outside in the UK?
Which? says to wait until mid to late May before you plant outdoors. The RHS wants nights above 7°C for tender plants, and nights above 10°C are the better test for tomatoes. A warm April afternoon is not that test.
What if nothing comes up?
Check the moisture below the surface and the date on the packet. Sow again within two weeks if the season still allows it, which is how the RHS suggests you recover a failed sowing. A few seeds on damp kitchen paper, at the same temperature as the tray, show whether the envelope is alive. If the date is already the expiry month, replace the packet.

Related pages

Tomato seeds

Vegetable seeds

Vegetables to sow in autumn UK: hardy October sowing

Best vegetable seeds UK for the crop you are sowing

What to look for on a vegetable seed packet in the UK

F1 or open-pollinated vegetable seeds: which to buy

Sources

Public UK sources named for this comparison. Updated October 2026.

  1. Seed Marketing Regulations 2011 (retrieved October 2026)
  2. Explanatory memorandum to the Seed Marketing Regulations 2011 (retrieved October 2026)
  3. GOV.UK, apply to have seeds certified for marketing in England and Wales (retrieved October 2026)
  4. Defra plant health portal, plant varieties and seeds FAQ (retrieved October 2026)
  5. RHS, F1 hybrids (retrieved October 2026)
  6. RHS, lettuce (retrieved October 2026)
  7. GOV.UK, Seed Potato Classification Scheme (retrieved October 2026)
  8. Consumer Rights Act 2015, section 11 (retrieved October 2026)