Name: watercress, garden cress, broadleaf cress, Nasturtium officinale.
Height: up to 15cm.
Plant type: perennial.
Climate: all climates.
Soil: moist, well-drained soil enriched with organic matter.
Position: full sun or part shade.
Flowers: clusters of small white flowers in spring and early summer.
Foliage: small-to-medium, round and lightly crinkled.
Feeding: fertilise regularly with a liquid plant food.
Watering: water regularly to keep the soil moist.
As its name implies, watercress is an aquatic or semi-aquatic plant. It’s found growing naturally in shallow waterways. The fleshy stems and leaves form a dense carpet on the surface of the water, and clusters of small white flowers appear in spring and early summer. Despite its botanical name, Nasturtium officinale, it is not related to nasturtium. It is a member of the brassica family and closely related to mustard and wasabi.
Watercress grows readily in the wild. In many areas it’s classed as a weed and may be contaminated with liver fluke – a small parasitic worm that typically occurs in creeks and waterways downstream from where cattle and livestock graze. This worm can infect humans and cause acute or chronic disease, so it’s best not to forage for wild watercress, especially if the water source is close to livestock.
The shoots and leaves are sharp and peppery and are ideal in salads, sandwiches or as a garnish. They can also be used to flavour soups and broths.
Watercress thrives in a moist environment. You can grow it in water, but it will also grow happily in the garden or pots provided the soil is well drained and kept consistently moist. Despite the fact it grows in water in the wild, watercress will not tolerate waterlogged soil or stagnant water – planting in these conditions can lead to root rot.
Seeds can be sown at almost any time of the year, but ideally late summer or early autumn. Sow seeds directly into garden beds or pots enriched with compost and they will germinate in 7-10 days. Water regularly to keep the soil moist. If growing in a pot, place the pot inside a larger vessel and keep it topped up with water.
Watercress needs minimal care once established in a pond or aquatic environment. However, if it’s growing in the ground or pots, it will need regular watering to keep the soil moist.
To ensure good growth, watercress needs to be watered regularly – do not allow the soil to completely dry out. Feed often throughout the growing season with an organic liquid fertiliser.
Watercress is usually ready for harvest eight to ten weeks from sowing. Snip stems near the base of the plant, leaving behind at least one pair of leaves on each stem to encourage more growth. Only harvest as needed, as watercress does not store well.
Harvest before flowering as this tends to alter the flavour profile, with leaves more bitter and less peppery.
Watercress is not especially prone to pests or disease. Snails and slugs may feed on developing seedlings but can be controlled with organic baits or barriers. As a member of the brassica family, the cabbage moth or small cabbage white butterfly may find the leaves appetising, but these can be controlled with a fine-gauge exclusion net or a suitable insecticide.
Grow plants from seed or seedlings. Watercress can also be propagated from stem cuttings. To do this, cut a piece of stem below a node (the bump along the stem where a leaf emerges), remove a few of the lower leaves, and place in a glass of water. Roots will form and once they are 5-7cm long, then transplant into the garden or pots.
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Wasabi: a lush evergreen perennial with pungent rhizomes that are popular in Japanese cuisine.
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