Watercress

Nasturtium officinale W.T.Aiton

Perennial
Semi-aquatic
Naming trap: not garden nasturtium

Pet & Human Safety

Toxic to people and pets

Human edibility

Edible

Edible parts

leaves and stems (dime-sized dark green leaves, picked at any time of year per Utah State University Extension)

Hazardous parts

Not yet checked.

Preparation

commonly eaten raw when grown in clean, controlled conditions, but RAW watercress: especially wild-harvested or grown in water exposed to livestock grazing runoff: is a documented transmission route for Fasciola (liver fluke) infection; CDC specifically advises against eating raw watercress and other freshwater plants from uncontrolled sources

Hazard type

parasitic infection risk (Fasciola/liver fluke) from contaminated raw watercress, not a plant-toxicity hazard

Hazard route

ingestion of raw, contaminated plant material

How complete this information is

The safety information on this page is partial. Where a source covers a point, it is shown; where none does, the page says so.

Toxic to pets

Confirmed toxic to dogs, cats, and horses on ASPCA's own dedicated page for this exact species: this is the true aquatic watercress, not the unrelated garden nasturtium (Tropaeolum majus), which ASPCA and most sources treat as non-toxic/edible. Do not let the two get confused by common name.

Patent / trademark

not applicable

Look-alike warning

Could be mistaken for Garden/edible-flower nasturtium (Tropaeolum majus, family Tropaeolaceae), an unrelated plant grown for orange/yellow flowers and peppery leaves. To tell them apart: Different families entirely: true watercress (this species, Nasturtium officinale, family Brassicaceae) is an aquatic/semi-aquatic crop; garden nasturtium is a terrestrial flowering annual.. Even NC State Extension's own plant-lookup page for 'nasturtium officinale' resolves to Tropaeolum majus's content: a real source-level trap, not just a common-name coincidence. Any growing or toxicity data sourced under a plain 'nasturtium' search needs the scientific name double-checked before being applied here.

Poison control

If someone has collapsed, cannot be woken, is having a seizure or has trouble breathing, call 911 now. For any other possible poisoning, call Poison Help: 1-800-222-1222.

Emergency number source: U.S. federal law (47 U.S.C. § 251(e)(3)), read 2026-10-07.

Naturalist Lore

Historical Background & Breeding Lore

The history of this plant and its name, and how it was bred, where we have them.

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Care

Hardiness zones: Perennial semi-aquatic herb, grown year-round where water conditions allow.
Water needs: very high: must be kept consistently saturated or grown submerged/in shallow moving water; this is not a typical garden-soil-moisture crop
Family: Brassicaceae (mustard family)

Soil & Drainage

Pruning & Flush Rhythm

Feeding Schedule

How to prepare the soil, when and what to feed, and how and when to prune where that applies.

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