Vegetable · Brassicaceae
Watercress
Nasturtium officinale
Give watercress cool, clean, moving water and it rewards you with a peppery harvest from spring right through fall, even on your first try.
Full sun
Every 1–3 days
32–77°F · 0–25°C
50–60 days
Overview
Watercress makes a lovely first edible to try, and it forgives more than you might expect. This fast-growing green carries a bright, peppery bite that lifts a salad or a sandwich, and it belongs to the mustard family with cabbage and radish rather than the climbing garden nasturtium people often mix it up with. You will find it growing wild along the edges of cool, clean streams across much of the temperate world.
The one thing it really asks of you is steady water. Its roots like to stay wet all the time, happiest in flowing spring water, though the plant settles just as gladly into a muddy bank or a pot standing in a tray of water. Keep that water cool and moving, and you will be picking watercress almost faster than it can regrow.
Few edibles are this easy to keep happy, so take heart. Pinch the shoots often and the plant answers by bushing out and staying tender. If the water warms or goes still and the leaves turn bitter, that is not failure, just a signal to cool things down, and the plant bounces right back once you do.
Care
The short version: keep cool, clean water around the roots at all times, offer full sun to a little shade, and pick often so the leaves stay tender and the plant holds off flowering. Do that and watercress mostly looks after itself.
Light
Watercress is happy in full sun to partial shade. Full sun gives you the fullest, heaviest growth, though a little afternoon shade is a kindness in summer because it keeps both the water and the leaves cooler.
Water
This is the part that matters most, so give it your attention. The roots need to stay submerged or in constantly saturated soil and should never dry out, even briefly. Cool, clean, flowing or spring water is ideal, and in a container you can stand the pot in a tray of water and refresh it every 1 to 3 days to keep it cool, clean, and full of oxygen.
Soil
Plant it in rich, mucky loam at a water's edge, or in a soil-filled pot standing in water. It copes with a generous pH range from 6.5 to 8.0, leaning a touch toward the neutral-to-alkaline side that echoes its native limestone streams.
Temperature
Watercress is a cool-water plant that stays comfortable from about 32°F to 77°F (0°C to 25°C). It takes frost in stride but tends to bolt and turn bitter once the water climbs much above that range, so a bit of summer shade and cool water keep it content.
Humidity
As an aquatic plant it enjoys humid air, from 70% up to nearly 100%. The standing water around its roots usually keeps the air moist enough on its own, so this is one thing you can happily forget about.
Feeding
In clean flowing water the plant feeds itself, so you can skip fertilizer with a clear conscience. In a container, offer a dilute balanced liquid feed monthly through spring and summer, when still water cannot quite supply everything it needs.
Pruning
Pinch and harvest the shoot tips often, and the plant thanks you with bushy, tender growth. As soon as flower stalks appear, snip them away, since flowering turns the leaves bitter and tells the plant to slow down.
Repotting
Lift and divide the mat about once a year, or a little sooner if the stems crowd together and new growth slows. Stems creeping over the edge of the tray are a friendly reminder that it is time to give the plant fresh room.
Size & spacing
Plants stay low, reaching only 4 to 20 inches (10 to 50 cm) tall, but they spread sideways into a mat 12 to 35 inches (30 to 90 cm) across. Give that spread some room to wander, or thin it now and then so the water keeps flowing through.
When to plant
Watercress loves the cool halves of the year and grows hard through spring and fall, easing off when summer heat arrives. Surface-sow the seed in late winter to early spring, move young plants outside once hard frost has passed, and pick the leaves from spring through fall, or all year where the water stays cool and moving.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Late winter to early spring, surface-sown on constantly moist medium
- Plant: Spring after danger of hard frost, or fall in mild-winter regions
- Harvest: Harvest leaves spring through fall (year-round in mild flowing water); small white cross-shaped flowers appear late spring to summer
Hardiness
USDA hardiness zones: 4–10
Temperature: down to -34°C
Troubleshooting
Almost every watercress hiccup comes back to the water or the weather, so there is rarely much mystery to solve. Warm, still water and summer heat cause most of it, and the leaves give you an early heads-up. Look for what matches below and gently correct the conditions before the whole mat suffers.
Leaves fading to pale yellow on a weary mat
This usually traces back to warm, still water. When the water stops moving it loses oxygen and heats up, and the oldest leaves are the first to go pale. Refresh or circulate the water to keep it cool, give the plant some partial shade through the summer heat, and if it lives in a container, offer a dilute balanced fertilizer to bring the color back.
Fix:
- Refresh or circulate the water to keep it cool and oxygenated
- Move to partial shade during summer heat
- Apply a dilute balanced fertilizer when grown in containers
Flower stalks rise and the leaves grow harsh and bitter
This is bolting, and heat is the trigger. Once the water warms past about 75°F (24°C), the plant sends up flower stalks, the leaves shrink, and that friendly peppery bite turns sharp and harsh. Pinch out the flowering stems, move the plant into shade with cooler water, and if summer has truly taken over, simply start again from stem cuttings once the weather cools. It comes back easily.
Fix:
- Harvest and pinch out flowering stems
- Provide shade and cooler water
- Restart from stem cuttings in the cooler season
Twisted leaves with clustered insects or small shot-holes
Two pests cause most of this. Aphids cluster on the leaf undersides and twist the new growth, while flea beetles nibble the little round holes that speckle a leaf like buckshot. A strong jet of water knocks both off, and cutting away any badly chewed shoots sets the plant right again.
Fix:
- Dislodge pests with a strong jet of water
- Remove and discard heavily infested shoots
Toxicity
Here is a reassuring one: watercress is food, not a hazard. It is safe for cats, dogs, horses, rabbits, livestock, birds, and people, with no toxin anywhere in the plant. The only thing to watch is for people, and it comes down to where the cress grew rather than anything about the plant.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Cats have nothing to fear from watercress. A curious nibble does no harm at all, though the peppery leaves rarely tempt them for long.
Dogs None
Dogs are safe with watercress, leaves and stems alike. A dog that wolfs down a big mouthful might get a little harmless gas, and nothing worse than that.
Horses None
Horses can graze watercress without any worry. The sharp mustard tang tends to keep them from eating much of it in the first place.
Rabbits Safe
Rabbits can enjoy watercress as part of a mixed green diet. Bring it in slowly, the way you would any new leafy vegetable, so their gut has time to adjust.
Livestock Safe
Cattle, goats, and sheep can browse watercress safely. It holds no toxin that would trouble grazing stock.
Birds Safe
Backyard hens and other birds can peck at the tender leaves with no ill effect, and the greens add a welcome bit of variety to their feed.
People Safe
Watercress is a nourishing salad green, good raw or cooked. The one real catch is with wild plants, since cress foraged from water grazed by livestock can carry liver fluke parasites, so cook wild-harvested cress or grow your own in clean water before eating it raw.
Food-safety note for people (not pet toxicity): wild watercress from water that may be contaminated by grazing livestock can carry liver fluke (Fasciola) larvae and waterborne pathogens. Cook wild-harvested cress or grow it in clean, uncontaminated water before eating it raw.
Varieties
Most of the watercress you grow will simply be the wild species, but a couple of named types are worth getting to know.
Improved Broad Leaved
A cultivated strain chosen for larger, broader leaves and a fuller harvest than the wild plant offers.
Nasturtium microphyllum (one-row, small-leaved watercress)
A close relative with smaller leaves and seeds set in a single row, which crosses freely with true watercress wherever the two grow together.
How to propagate
Watercress multiplies so eagerly that stopping it is the harder job, whether you root a few cuttings in a glass of water or scatter seed over damp ground.
Stem cuttingsEasy
Any time during active growth, best in spring or fall · 1 to 2 weeks
Cuttings are the fastest way to get started, and you can take them any time the plant is growing, with spring and fall giving the nicest results. Snip stems about 4 to 6 inches (10 to 15 cm) long and stand them in a glass of water or press them into wet soil. They root at the nodes within 1 to 2 weeks, and you are on your way.
SeedEasy
Spring, in cool moist conditions · 2 to 3 weeks to germinate and establish
Seed does well in the cool, damp days of spring. Scatter the tiny seeds across the surface of a constantly moist medium instead of burying them, since they need light and must never dry out. Give them 2 to 3 weeks in cool temperatures to sprout and settle in.
Myths
Wild watercress is always fine to eat raw straight from the stream.
Cress taken from water where livestock graze can carry liver fluke larvae and other waterborne organisms you simply cannot see. The safe habit is easy: cook wild-harvested cress, or grow your own in clean water, before eating any of it raw.
Edible watercress and the ornamental garden nasturtium are the same plant.
They share a peppery flavor and part of a common name, and that is where the resemblance stops. The edible one is Nasturtium officinale in the mustard family, while the climbing garden nasturtium is Tropaeolum majus, a wholly separate genus.
Watercress needs deep running water and cannot be grown at home.
Flowing spring water is the ideal, but it is far from essential. A pot of rich soil standing in a tray of water, kept wet and refreshed, gives you a steady supply right on a windowsill or patio.