Watercress

Sun

Full sun to partial shade; afternoon shade helps keep growth tender in hot weather.

Water

Keep the roots constantly wet with clean water. Cool, gently moving water is ideal; container-grown plants need frequent water changes.

Soil

Fertile, moisture-retentive soil or loam-based compost, preferably neutral to slightly alkaline; never allow it to dry out.

Height

0.5-1.5 ft (0.15-0.45 m)

Spread

1-3 ft (0.3-0.9 m), spreading farther where stems can root freely

Flowers

Small white flowers in clusters from late spring through summer.

Foliage

Succulent, hollow stems carry glossy green leaves divided into rounded leaflets, with a larger terminal leaflet. Evergreen in mild conditions, but growth may die back in hard frost.

Growth

Fast in cool, wet conditions

Care needed

Medium

• Pollinators
• Low allergen
• Edible

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

   full size

About 2 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Native to

the UK

Invasive in

the US and Australia

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Grow edible plants in a dedicated container supplied with drinking-quality water, away from livestock runoff, pond water and animal waste.
• Stand a pot of loam-based compost in a water tray, keeping the water near the compost surface without submerging the leafy shoots.
• Replace tray water every two or three days, more often in hot weather, and remove fallen leaves.
• If growth becomes pale, apply a dilute balanced fertiliser labelled for edible crops, following its container-feeding directions.
• Move containers into afternoon shade during hot spells and protect small pots from freezing solid.
• Keep rooted stems, seeds and discarded cuttings out of drains and natural waterways.

Pruning. Pinch or cut shoot tips regularly during active growth, leaving several leafy joints to regrow. Remove flower stems as they appear if tender leaves are your priority, and cut out damaged or decaying growth promptly.

Pick leafy shoot tips once plants are well rooted and have several healthy stems, usually a few weeks after rooted cuttings are planted. Snip tender shoots about 4-6 in (10-15 cm) long, preferably before flowering, and wash them thoroughly. Do not harvest wild watercress or plants exposed to livestock runoff: raw leaves can carry liver fluke and other pathogens, which washing alone does not reliably remove.

Early spring

Clean containers, replace exhausted compost and start seed or rooted cuttings under protection.

Spring

Move established plants outdoors as conditions allow, keeping roots wet and protecting tender new growth from hard frost.

Late spring

Begin regular tip harvests and remove developing flower stems.

Summer

Provide afternoon shade in hot weather, refresh water frequently and check for aphids and caterpillars.

Autumn

Take rooted cuttings to renew tired plants and continue harvesting fresh growth in cool weather.

Winter

Keep roots wet but remove decaying shoots; shelter containers where prolonged freezing would freeze the root ball solid.

• Grow in a dedicated water-holding container beside the kitchen for convenient harvesting.
• Use its low, glossy foliage as a contained green edge in a potager.
• Place a shallow growing tub among other herb containers to add contrasting leaf texture.
• Use in an isolated ornamental water feature for trailing growth, but do not eat plants supplied with untreated pond water.

Garden styles it suits: Potager (kitchen garden), Edible landscape, Homestead, Cottage garden, Small-space and Bog garden.

Plant it with: Chives, Parsley, Lettuce and Mint.

Wildlife: Flowers attract small bees and flies, while cabbage white butterflies may lay eggs on the leaves. Dense growth can shelter aquatic invertebrates, but escaped plants may crowd waterways.

• Aphids cluster on soft shoots: rinse them off with clean water and remove heavily infested tips.
• Cabbage white caterpillars chew leaves: inspect regularly, hand-pick caterpillars and use fine insect mesh if needed.
• Yellowing or rotting stems develop in warm, stagnant water: remove affected material, clean the container and refresh the water more frequently.
• Hot weather encourages flowering and tougher, more pungent leaves: provide afternoon shade, trim flowering stems and renew plants from healthy cuttings.

Watercress is edible for people when correctly identified and grown with safe water. It is considered toxic to cats, dogs and horses: leaves and stems contain mustard-oil compounds that can cause vomiting, diarrhoea or abdominal discomfort if eaten. Keep pets and grazing animals from eating it, and seek veterinary advice after a substantial ingestion or if symptoms occur.

Where it spreads. Introduced watercress can form dense mats in streams and springs, particularly in the western United States, New Zealand and parts of southeastern Australia. It can spread aggressively through rooting stem fragments and seed; contain it and check local restrictions before planting near water.

• Fool's watercress (Helosciadium nodiflorum)

  It has more noticeably toothed leaflets and tiny white flowers in umbrella-shaped clusters, rather than watercress's four-petalled flowers in elongated clusters.

• Spotted water hemlock (Cicuta maculata)

  This deadly poisonous wetland plant grows much taller, with sharply toothed, pointed leaflets and umbrella-shaped white flower heads. Watercress has rounded leaflets and four-petalled flowers;

• Great yellowcress (Rorippa amphibia)

  It bears yellow rather than white flowers and usually has longer, more elongated leaves. Flowerless aquatic mustard relatives can be difficult to distinguish.

Nasturtium comes from Latin words meaning 'nose-twister', referring to the pungent taste, while officinale indicates a plant traditionally used in medicine.

Propagation. Root healthy stem cuttings in clean water, then plant them into wet compost, or divide rooted clumps in spring. Seed can be surface-sown on saturated compost; keep it moist and transplant seedlings once they are large enough to handle.

Accepted botanical name

Nasturtium officinale

In the US and Canada

Introduced in Alaska, Canada, the lower 48 states, Puerto Rico, St. Pierre and Miquelon and US Virgin Islands.

Native range

Afghanistan, Albania, Algeria, Austria, Azores, Baleares, Belgium, Bulgaria, Canary Is., Cape Verde, Central European Rus and Chad.

Measured

Soil pH 6.4 to 8. Average height 40 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.