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How to Grow Watercress Canada | Care, Pests & Disease Control

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Watercress (Nasturtium officinale)

A dense bed of round-leaved watercress — “Nasturtium officinale kz06” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY-SA 4.0. Source: Wikimedia Commons

8 sources cited · Verified

The short answer

Site
soil pH 6.5–7.5
Biggest risk
Watercress leaf spot

Watercress (Nasturtium officinale) — herbaceous perennial.

This crop carries an unusually heavy problem load: 2 diseases, 6 pests and 0 nutrient issues are documented for it, so most of the effort in growing it well goes into prevention.

Core growing advice on this page is checked against named horticultural and university-extension sources — see References.

Diseases

A flowering mat of watercress spreading over wet ground — “Nasturtium officinale kz21” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY 4.0. Source: Wikimedia Commons
“Nasturtium officinale kz21” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY 4.0. Source: Wikimedia Commons.
Watercress leaf spot (causal agent not yet confirmed)
Watercress root rot (causal agent not yet confirmed)

Pests

A flowering mat of watercress spreading over wet ground — “Nasturtium officinale kz21” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY 4.0. Source: Wikimedia Commons
“Nasturtium officinale kz21” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY 4.0. Source: Wikimedia Commons.

Aphididae (various spp.)

Slugs

Gastropoda (slugs, various spp.)

Snails

Gastropoda (snails, various spp.)

Glasshouse whitefly adult on a leaf — Sanja565658, CC BY-SA 3.0
Sanja565658, CC BY-SA 3.0
Glasshouse whitefly

Trialeurodes vaporariorum

Two-spotted red spider mite with silk threads, magnified — Gilles San Martin, CC BY-SA 2.0
Gilles San Martin, CC BY-SA 2.0
Glasshouse red spider mite (two-spotted spider mite)

Tetranychus urticae

Cabbage caterpillars

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

Quick Facts

A dense bed of round-leaved watercress — “Nasturtium officinale kz06” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Nasturtium officinale kz06” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.
Factor Value
Soil pH 6.5 - 7.5
Germination temp 10C
Drainage Clay, Loam, Sand; humus-rich, permanently wet or saturated soil (aquatic/bog conditions)
Lifecycle herbaceous perennial
Edible parts leaves

At a Glance

Watercress growing in a shallow flowing stream — “Nasturtium officinale kz05” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Nasturtium officinale kz05” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.
Nasturtium officinale Watercress Watercress leaf spot (c… Watercress root rot (ca… Aphids Slugs Snails Glasshouse whitefly Glasshouse red spider m… Cabbage caterpillars DISEASES PESTS

Soil & Growing Conditions

Watercress growing in a shallow flowing stream — “Nasturtium officinale kz05” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Nasturtium officinale kz05” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.

Soil pH range

6.5 7.5

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

Growth Stages

Small white watercress flowers above the foliage — “Berro (Nasturtium officinale) en México II” by Juan Carlos Fonseca Mata is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Berro (Nasturtium officinale) en México II” by Juan Carlos Fonseca Mata is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.
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 8-15C (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

A dense bed of round-leaved watercress — “Nasturtium officinale kz06” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Nasturtium officinale kz06” by Krzysztof Ziarnek, Kenraiz is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.

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)

References

  1. country=INTL

  2. country=UK

  3. country=UK

  4. Tier 1. 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.

  5. Directly fetched and verified. 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.

  6. Directly fetched and verified. 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. Directly fetched and verified (canonical URL differs from requested URL /biodiversity/slugs -> redirects to /biodiversity/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.

  8. country=USA

8 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.

Frequently Asked Questions

What soil pH do watercress need?

A pH of about 6.5–7.5. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.

What problems affect watercress?

Our data links 2 diseases and 6 pests to this crop. See the sections above for each one and how to manage it.

Plan next season before the problems start

Short-season growing is arithmetic before it is technique: days to maturity against frost-free days decides what will finish at all. The Canada Garden Planner does that subtraction for your region before you sow.

Get the Canada Garden Planner →

Instant PDF download · Written for Canadian growing conditions

SoilCommander Editorial Team

Canadian vegetable growing guides · Checked against provincial agriculture & university extension guidance

Every SoilCommander guide is written and maintained by our editorial team for real Canadian growing conditions, and checked against provincial agriculture and Canadian university extension guidance, and against frost-date and growing-season data, before publication.

Vegetable Growing Guides Canada

Last verified 2026-09-02

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