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How to grow watercress from seed

Updated: 21 October 2026

You have a watercress packet and a tray of compost, and another brand’s card disagrees about depth and warmth. How to grow watercress from seed, for Nasturtium officinale, comes down to moisture and to the instruction on the packet in your hand. Thompson & Morgan say do not cover the seed. Unwins’ Aqua page says 3 mm. Suttons’ Aqua card says 0.5 cm. Those are three UK instructions, not one average. The packets were chosen on the [watercress seeds comparison](/hub/herb-seeds/watercress-seeds). Peter F. used those listings and the UK seed-firm notes. There was no germination trial. A qualifying purchase can earn a commission at no extra cost to you.

You have a watercress packet and a tray of compost, and another brand’s card disagrees about depth and warmth.

Our top picks

Just Seed Just Seed watercress, 6,000 seeds

Best overall

Just Seed Just Seed watercress, 6,000 seeds
8.6/10about £3.50
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JustSeed JustSeed watercress, 600 seeds

Best value

JustSeed JustSeed watercress, 600 seeds
8.4/10about £3.10
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Mr Fothergill's Mr Fothergill's Watercress Aqua

Alternative

Mr Fothergill's Mr Fothergill's Watercress Aqua
8.2/10about £3.29
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On this page
  1. 1.Surface or a thin cover
  2. 2.Temperature and the month on the listing
  3. 3.From a sprout to a cut
  4. 4.If nothing comes up

Surface or a thin cover

Watercress seed is small. Burying it under a centimetre of dry compost is a common way to lose it. Thompson & Morgan say surface-sow and leave the seed uncovered, in March and April, with germination within 14 days at about 8–15°C. Follow that when your packet says the same, or when it says nothing. Unwins’ Aqua page says sow at 3 mm with a very thin cover, then thin to 10 cm. Suttons’ Aqua card says 0.5 cm deep and cover, with germination in about 7 days. If you are holding Just Seed, do not borrow Suttons’ depth. Just Seed’s amazon care text in this set gives no millimetre figure. If your packet names a depth, use that depth. If it does not, leave the seed on wet compost and do not let the surface crust.

Temperature and the month on the listing

UK writing runs from about 8°C to about 18°C, and the month depends on the card. Love The Garden says sow outdoors once the soil is at least 8°C, and start indoors from mid-January to the end of March at 8–15°C. Thompson & Morgan use that band for March and April. Other cards sit at 16–18°C. A kitchen at 21°C and dry is outside those bands. These listings do not share one calendar. Just Seed’s attribute says spring. Mr Fothergill’s says summer. Batlle says February to July. If the packet names a window, that is the window you bought. If it only says spring, hold the compost near 8–15°C. One UK review of JustSeed B079593G52 reported December germination on a kitchen windowsill. That is one packet, not a promise for every Aqua bag.
Just Seed Just Seed watercress, 6,000 seeds

Testsieger

Just Seed Just Seed watercress, 6,000 seeds
8.6/10about £3.50
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From a sprout to a cut

Love The Garden spaces plants 10–15 cm apart. Unwins’ Aqua page thins to 10 cm. Harden indoor plants off over 10–14 days before they live outside. Cut when you have leaves you want to eat. A UK review of the 600-seed packet described cutting stems and leaving a couple of inches so the plant regrew. Mr Fothergill’s bullets also say baby leaves or mature plants. Take the flowers off if you want leaves. You can let one plant flower. Do not let the whole pot flower if the point was salad.

If nothing comes up

A bare tray is usually dry compost, old seed, or a depth the packet did not ask for. On the 6,000-seed Just Seed packet, one buyer said it did not grow, one saw a late start, and one found seed that seemed dated and stuck together. On Mr Fothergill’s Aqua, a repeat buyer had no germination yet in seed compost. None of these packets states a germination figure, so you cannot hold them to 7 days from a Suttons card you do not own. Sow again from the same bag if most of the seed is unused and you can keep the surface wet at 8–18°C. Replace the bag if the seed was clumped and dull, or if the title was never watercress. If you are ill after eating leaves, use NHS services.

Common questions

Do I bury watercress seed?
Only as deep as the packet says. Thompson & Morgan say do not cover it. Unwins’ Aqua page says 3 mm with a very thin cover. Suttons’ Aqua card says 0.5 cm and cover. If your packet is silent, surface-sow on wet compost. Do not average those figures into one depth for every brand.
What temperature should I aim for?
About 8–15°C is the band Thompson & Morgan and Love The Garden use. Other UK cards press the seed in at 16–18°C. Outdoors, wait until the soil is at least 8°C. A hot, dry windowsill above that range is a worse bet than a cooler room where you can keep the compost wet.
How long until it germinates?
Published UK notes say within 14 days, about 7–14 days, or one to two weeks, depending on the firm. Suttons’ Aqua card says about 7 days for that packet. Just Seed’s listings in this set do not promise 7 days. If you see nothing after a fortnight, check dryness and seed condition before you blame the calendar.
Can I sow on a windowsill in winter?
One UK review of JustSeed B079593G52 reported germination in December on a kitchen windowsill. That is a single account. You still need moisture and something close to the 8–18°C band. It is not a promise for Unwins or Batlle, and it is not a reason to sow into a freezing porch.
When do I thin, and what do I do with flowers?
Thin to about 10 cm on the Unwins Aqua guidance, or 10–15 cm on Love The Garden. Harden indoor plants off over 10–14 days before they go outside. Remove flowers if you want more leaves. Leave a couple of inches when you cut, which is how one reviewer got regrowth rather than a single picking.
Which listing month do I follow if they disagree?
Follow the packet you bought. In this snapshot Just Seed says spring, Mr Fothergill’s says summer, and Batlle says February to July. Those attributes are not a single UK season. Where the packet is vague, use 8–15°C and a wet surface, which is the Thompson & Morgan reading, rather than a month copied from a different brand.

Related pages

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Best watercress seeds for your pot, count, or Aqua

Watercress vs garden cress: which seed do you mean

Sources

Public UK sources named below. amazon.co.uk prices, stars and review counts on these eight listings were read for this comparison. Page updated 21 October 2026.

  1. RHS, Nasturtium officinale (retrieved 21 October 2026)
  2. Thompson & Morgan, how to grow watercress (retrieved 21 October 2026)
  3. Love The Garden, watercress (retrieved 21 October 2026)
  4. Seed Marketing Regulations 2011, Schedule 3 (retrieved 21 October 2026)
  5. GOV.UK, organic food: approved UK control bodies (retrieved 21 October 2026)
  6. GOV.UK, watercress product specification (retrieved 21 October 2026)
  7. NatureScot, foraging for wild plants (retrieved 21 October 2026)
  8. FSA-recognised watercress hygiene guide (2017) (retrieved 21 October 2026)