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How To Grow Watercress

Nasturtium officinale

Low growing and trailing European perennial Nasturtium officinale, a member of the Mustard Family, is naturalized in springs and wet ground in temperate climates.

Though easily grown from seed, it is usually propagated by bits of stem which readily take root in wet soil and need no further attention. Its natural season is from mid-autumn until spring. After its flower buds appear the leaves become too rank in flavor to be edible.

Watercress has many culinary, decorative, and medicinal uses.

Growing the Herb Watercress

It can easily be grown in containers that are dug into the surface of the soil and filled with fresh water on a frequent basis.

It is also easily grown indoors in individual pots that are placed in a tray of water. Start plants with seed by sowing lightly in pots filled with a mix of garden soil, limestone, and organic compost.

Keep moist at all times, keeping the plants in a partially shaded area. As soon as seedlings are large enough to move, in April or May ideally, they can be transplanted to stream or creek banks where they will establish themselves and create a bed that will provide cut watercress every spring and fall.

Growing Cultures

Outdoors, containers, and hydroponics.

Plant Height

Watercress plants grow to a height of 6 to 24 inches (15 - 60cm).

Plant Spacing

Watercress plants should be spaced 9 to 12 inches (22 - 30cm) apart.

Preferred pH Range

Watercress will grow in a pH range between 6.0 (mildly acidic) and 7.5 (mildly alkaline) with a preferred pH range between 6.5 and 7.5.

Propagation

Sow watercress seed indoors in sunny location or under plant grow lights six weeks before last frost. Watercress propagates well through stem cuttings.

Seed Germination Period

Watercress seeds will germinate in soil in approximately 7 to 14 days, but can germinate in as few as 5 or 6 days in dedicated propagation media such as Oasis Rootcubes, Rapid Rooters, or Grodan Stonewool.

Number of Seeds per Gram

There are approximately 5,000 watercress seeds per gram.

Soil Requirements

Watercress grows well in rich, fertile soil.

Alternative Growing Media

Soilless potting mixes (Pro-Mix, Sunshine Mix, etc.), perlite, vermiculite, rockwool, coco peat, Oasis Rootcubes.

Sun & Lighting Requirements

Watercress grown outdoors prefers full sun but tolerates some shade.

Watercress will grow indoors satisfactorily under standard fluorescent lamps, and exceptionally well under high output T5 fluorescent plant lights, compact fluorescent, or high intensity discharge (metal halide or high pressure sodium) plant growing lights. Keep standard fluorescent lamps between 2 and 4 inches from the tops of the plants, high output and compact fluorescents approximately one foot above the plants, and HID lights between 2 and 4 feet above the plants, depending on wattage.

Have an oscillating fan gently stir seedlings for at least 2 hours per day to stimulate shorter, sturdier, and more natural plant habit.

USDA Hardiness

Perennial. Zones 9a to 11.

Water Requirements

Above average water needs. Suitable for bogs and watergardens. Thrives in hydroponics.

Potential Plant Pests and Diseases

Watercress can be susceptible to whitefly and spider mites, but has minimal disease issues.

Special Notes

Grown for aromatic foliage. Requires large amounts of water.

Buy Watercress Seeds by Botanical Interests

Heirloom Watercress Seeds
Snappy, peppery flavor added to salads & omelets. Classic ingredient in finger sandwiches served at English high tea.