Watercress
Nasturtium officinale
Also known as: Watercress, Common Watercress
'Nasturtium' is believed to come from the Latin 'nasus tortus' (twisted nose), referring to the pungent, peppery smell and flavour that causes an involuntary wrinkling of the nose. Note that 'Nasturtium officinale' (watercress) is unrelated to the garden Nasturtium (Tropaeolum majus), though both are edible. 'Officinale' indicates it was a recognised medicinal herb. Watercress is a semi-aquatic, perennial herb native to Europe and Asia, now naturalised in clean, cold, flowing streams and freshwater springs throughout southern Australia. It is among the most nutrient-dense foods available anywhere. It grows in dense, spreading mats of floating and creeping stems, rooting at every node, in and along the margins of shallow, fast-flowing, clear water.
When to Forage
Year-round; best in cool months (autumn through spring) when plants are most vigorous.
Cautions
Very important: watercress must be foraged only from clean, unpolluted, flowing water sources. It can harbour the liver fluke parasite (Fasciola hepatica) if growing in water where livestock (especially cattle and sheep) have access to the stream. Always cook watercress foraged from wild sources if there is any possibility of contamination, or consume only from verifiably pristine springs. Those on anticoagulant medication (warfarin) should be aware of the high vitamin K content. Those with thyroid conditions: watercress is a mild goitrogen – consume cooked rather than raw in large quantities.
Nutrition
Exceptional nutritional density. Very high in vitamins K, A (beta-carotene), C, and E. Contains vitamins B1, B2, B6, and folate. Rich in minerals: calcium, iron, magnesium, phosphorus, and potassium. Contains glucosinolates (including phenethyl isothiocyanate, PEITC – studied for anti-cancer properties). Protein content is high for a leafy green. Consistently ranked among the most nutrient-dense vegetables.
How to Identify
- Aquatic to semi-aquatic, mat-forming herb with round to oval, dark green leaflets arranged pinnately along the stem – typically one large terminal leaflet and two to four pairs of smaller side leaflets.
- Stems are hollow, semi-succulent, and root readily at each node when in contact with water or wet ground.
- Flowers are small, white, four-petalled – classic mustard family (Brassicaceae).
- Grows in running water, alongside springs, or in seeps where clean fresh water flows.
- Peppery, mustard-family flavour when a leaf is bitten.
Lookalikes
Grows in similar wet habitats; pale green, compound leaves superficially like watercress but with more pointed leaflets and a faint celery smell. Not typically toxic but not reliably edible; confusion with toxic relatives is the main risk.
Grows in similar wet habitats; similar pinnate leaves. Uncommon in Australia but its relatives may be present. Distinguished by more divided, finely cut leaves; a parsnip-like smell from the roots; and yellow-orange sap from a cut root. Never eat any watercress-like plant from wet areas without confirming it is the true Nasturtium officinale with the characteristic peppery taste.
How to Forage
Wade or crouch at the water's edge. Snap or cut stems just above the waterline or at a side branch. Collect only from fast-flowing, clear water distant from agricultural land or livestock access. Collect sufficient material and keep it cool and damp. Wash thoroughly. If in doubt about water quality – cook rather than eat raw.
Recipe — Watercress and Pear Salad with Toasted Walnuts
Ingredients: 3 large handfuls watercress (washed); 1 ripe pear, thinly sliced; 1/3 cup toasted walnuts; 2 tbsp extra virgin olive oil; 1 tbsp white wine vinegar; 1 tsp maple syrup; 1 tbsp tahini; salt and pepper. Method: If foraging from a wild source, briefly blanch the watercress for 30 seconds (skip if from a known clean source), then drain and cool. Arrange the watercress on a serving platter, layer the pear slices over the top, and scatter over the toasted walnuts. Whisk the olive oil, vinegar, maple syrup, tahini, salt, and pepper into a creamy dressing, drizzle over the salad, and serve.
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