How to Grow Watercress UK

When to Plant Watercress in the UK

When to plant watercress in the UK: in Southern England, sow mid January to late April. Find your area in the table below.

Region	Sow
Southern England	mid January to late April
Midlands	mid January to late April
Northern England	mid January to late April
Scotland	mid January to late April

Southern England - detail & sources

Love The Garden: sow from mid-January to the end of March under cover at a constant 8-15°C, or on moist compost in spring, planting out once frost risk has passed. A single window is applied uniformly across all four sub-regions since the sources give no UK-region-specific gradient; watercress is a British native rated H6 and hardy throughout the UK, and the early part of the window is a heated indoor sowing regardless of region.

Midlands - detail & sources

Love The Garden: sow from mid-January to the end of March under cover at a constant 8-15°C, or on moist compost in spring, planting out once frost risk has passed. A single window is applied uniformly across all four sub-regions since the sources give no UK-region-specific gradient; watercress is a British native rated H6 and hardy throughout the UK, and the early part of the window is a heated indoor sowing regardless of region.

Northern England - detail & sources

Love The Garden: sow from mid-January to the end of March under cover at a constant 8-15°C, or on moist compost in spring, planting out once frost risk has passed. A single window is applied uniformly across all four sub-regions since the sources give no UK-region-specific gradient; watercress is a British native rated H6 and hardy throughout the UK, and the early part of the window is a heated indoor sowing regardless of region.

Scotland - detail & sources

Love The Garden: sow from mid-January to the end of March under cover at a constant 8-15°C, or on moist compost in spring, planting out once frost risk has passed. A single window is applied uniformly across all four sub-regions since the sources give no UK-region-specific gradient; watercress is a British native rated H6 and hardy throughout the UK, and the early part of the window is a heated indoor sowing regardless of region.

Quick Facts

Factor	Value
Soil pH	6.5 - 7.5
Drainage	Clay, Loam, Sand; humus-rich, permanently wet or saturated soil (aquatic/bog conditions)
Lifecycle	herbaceous perennial
Edible parts	leaves

At a Glance

Soil & Growing Conditions

Soil pH range

6.5 7.5

Span reflects genuine variation between the cited authorities, not a single agreed figure.

Growth Stages

Stage	BBCH	Notes
Sowing and germination	0	Sow on moist compost in spring, or from mid-January to end of March in pots in a propagator or warm place at a constant 8-15°C (Love The Garden).
Planting into water culture	1	Plant out once frost risk has passed, or pot into a 30cm container of compost stood in a shallow tray of fresh tap water; top the tray up daily and change it completely every 1-2 days in warm weather (Love The Garden).
Leafy growth	3	Plants stay low at 10-50cm but spread 0.5-1m; they thrive in constantly wet, poorly drained conditions in full sun or partial shade (RHS).
Harvest and flowering	4	Cut leaves from about 4-6 weeks in containers stood in frequently refreshed water. Small white flowers open from late spring through midsummer; plants can be increased from rooted runners in spring (Love The Garden, RHS).

Harvest & Storage

When to pick: Cut-and-come-again: pinch out dime-sized dark green leaves at any time of year, ideally before flowering; peppery flavour is best in cooler spring and fall and deteriorates above 85°F (29.4°C)

Diseases

Watercress root rot (causal agent not yet confirmed)

Watercress leaf spot (causal agent not yet confirmed)

Pests

Glasshouse red spider mite (two-spotted spider mite)

Tetranychus urticae

Glasshouse whitefly

Trialeurodes vaporariorum

Aphids

Aphididae (various spp.)

Cabbage caterpillars

Pieris brassicae; Pieris rapae; Pieris napi; Mamestra brassicae; Plutella xylostella

Snails

Gastropoda (snails, various spp.)

Slugs

Gastropoda (slugs, various spp.)

Watercress, the Peppery Green That Wants Wet Feet

Round, peppery leaves

The round leaves carry a mustard-hot peppery bite and are ready to cut in four to six weeks.

A chalk stream native

Watercress grows wild in the shallow running water of clean British chalk streams.

It genuinely wants wet feet

RHS: watercress thrives in poorly drained ground -- at home, grow it in a pot stood in a water tray.

Small white flowers

Little white flowers open from late spring through midsummer above the foliage.

Low but wide-spreading

Plants stay just 10-50cm tall but spread to a metre, forming dense mats over wet ground.

References

1. GBIF - GBIF Backbone Taxonomy: Nasturtium officinale
2. Love The Garden - How to grow and care for Watercress (Nasturtium officinale)

   Sow seed on moist compost in spring and plant out young plants once all frost risk has passed; for an earlier start sow from mid-January to the end of March in pots or trays of moist seed compost, in a propagator or warm place covered with a plastic bag, held at a constant 8-15°C. For container culture, fill a 30cm pot with compost, sow or plant watercress, and stand it in a shallow tray of fresh tap water topped up daily and changed completely every 1-2 days in warm weather. Ready in about 4-6 weeks in containers stood in frequently refreshed water. LIVER FLUKE: avoid harvesting watercress from the wild, as plants may harbour liver flukes damaging to human health; any plants growing in water draining from fields where animals, particularly sheep, graze should not be eaten raw, though cooking the leaves destroys the parasite and makes the plant perfectly safe.

3. Royal Horticultural Society - Aphids: Identification and Control

   RHS explicitly does not recommend pesticide use against aphids; recommends tolerance, manual squashing, and encouraging/purchasing natural predators (ladybirds, hoverflies, lacewings, parasitoid wasps, earwigs) as biological control, especially under glass.

4. Royal Horticultural Society - Cabbage caterpillars
5. Royal Horticultural Society - Glasshouse red spider mite

   RHS factsheet on glasshouse red spider mite (two-spotted spider mite), naming tomato and strawberry among the host plants affected under glass or in a polytunnel.

6. Royal Horticultural Society - Glasshouse Whitefly: Identification and Control

   RHS explicitly distinguishes yellow sticky traps as a monitoring tool rather than a standalone control method, and notes traps also catch non-target parasitoid wasps -- a genuine trade-off between two control methods, preserved rather than simplified. No specific pesticide/insecticidal soap product is named on this page (RHS links out to a general pesticides statement instead), so none is recorded here.

7. Royal Horticultural Society - Nasturtium officinale | common watercress
8. Royal Horticultural Society - Slugs and Snails

   RHS explicitly advises against slug pellets (even organic) due to wildlife harm, and cites RHS's own controlled trial finding no damage reduction from physical barriers (copper tape, bark mulch, eggshell, grit, wool) -- while also noting some other studies have shown copper barriers to repel slugs, a preserved disagreement rather than a silently resolved one. Details Nemaslug (Phasmarhabditis hermaphrodita) biological control including application temperature range and its lack of effect on snails specifically.

9. Useful Temperate Plants - Nasturtium officinale

   Mirrors FAO Ecocrop. Fetched and parsed directly for the numeric soil pH range.

10. Utah State University Extension - How to Grow Watercress in Your Garden

10 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.