Vegetable · Brassicaceae
Watercress
Nasturtium officinale
Hand watercress cool, clean, moving water and it fires back a peppery harvest from spring straight through fall.
Full sun
Every 1–3 days
32–77°F · 0–25°C
50–60 days
Overview
Watercress grows fast and packs a bright, peppery punch that wakes up any salad or sandwich. It runs with the mustard family beside cabbage and radish, so shake off the mix-up with the climbing garden nasturtium. Out in the wild it thrives along the edges of cool, clean streams across much of the temperate world.
The water is what makes this crop such a thrill to grow. The roots crave constant wet feet, ideally in flowing spring water, and the plant roots away just as fast into a muddy bank or a pot set in a tray of water. Keep the water cool and moving and it grows almost quicker than you can pick it.
Count it among the most rewarding edibles going. Pinch the shoots often and it bushes out into thick, tender growth you can harvest again and again. Let the water warm up or go still, though, and it bolts, turns bitter, and thins out fast.
Care
The short version: keep cool, clean water at the roots at all times, give full sun to part shade, and harvest often to keep the leaves tender and hold off flowering.
Light
Watercress runs well in full sun to partial shade. Full sun pushes the heaviest growth, but slip it a little afternoon shade in summer to keep the water and the leaves cooler.
Water
Nail this and everything else falls into place. The roots have to stay submerged or in constantly saturated soil and can never dry out, not even briefly. Cool, clean, flowing or spring water is the goal, and in a container you just 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 into rich, mucky loam at a water's edge, or a soil-filled pot standing in water. It rolls with a wide pH span from 6.5 to 8.0 and leans toward the neutral-to-alkaline end that echoes its native limestone streams.
Temperature
Watercress is a cool-water plant that powers along from about 32°F to 77°F (0°C to 25°C). It shrugs off frost but bolts and turns bitter once the water climbs past that range, so summer shade and cool water keep it charging.
Humidity
As an aquatic plant it thrives on humid air, from 70% up to nearly 100%. The standing water around the roots usually keeps the air moist enough on its own, so this one barely crosses your mind.
Feeding
In clean flowing water the plant feeds itself, so skip the fertilizer entirely. In a container, hand it a dilute balanced liquid feed monthly through spring and summer, when still water cannot keep up.
Pruning
Pinch and harvest the shoot tips often to drive bushy, tender growth. The instant flower stalks appear, snip them out, since flowering turns the leaves bitter and tells the plant to wind down.
Repotting
Lift and divide the mat about once a year, or sooner when the stems crowd and new growth slows. Stems creeping over the tray edge are your green light to give it fresh room.
Size & spacing
Plants stay low at 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 room to roam, or thin it so the water keeps rushing through.
When to plant
Watercress hits its stride in the cool of spring and fall and eases off in summer heat. Surface-sow the seed in late winter to early spring, get young plants outside once hard frost has passed, and pick leaves from spring through fall, or all year long 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
Nearly every watercress hiccup traces straight back to the water or the weather, so the fixes come quick. Warm, still water and summer heat drive most of it, and the leaves flag the change early. Spot what matches below and set the conditions right before the whole mat slides.
Pale, yellowing leaves on a flagging mat
Point the finger at warm, still water. Once the water quits moving it loses oxygen and heats up, and the oldest leaves pale first. Refresh or circulate the water to cool it, shift the plant into partial shade through the summer heat, and hand it a dilute balanced fertilizer if it grows in a container.
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 rocket up and the leaves turn harsh and bitter
Call it bolting, and blame the heat. Once the water pushes past about 75°F (24°C), the plant throws up flower stalks, the leaves shrink, and the peppery bite turns harsh. Pinch out the flowering stems, move the plant into shade with cooler water, and restart from stem cuttings once the weather cools if summer runs away with it.
Fix:
- Harvest and pinch out flowering stems
- Provide shade and cooler water
- Restart from stem cuttings in the cooler season
Curled leaves with clustered bugs or tiny shot-holes
Two pests do most of the damage. Aphids pile onto the leaf undersides and twist the new growth, while flea beetles punch the small round holes that pepper a leaf like buckshot. Blast both off with a strong jet of water and cut away any shoots chewed past saving.
Fix:
- Dislodge pests with a strong jet of water
- Remove and discard heavily infested shoots
Toxicity
Great news for growers: watercress is a food crop, not a hazard. It comes up safe for cats, dogs, horses, rabbits, livestock, birds, and people, with no toxin anywhere in the plant. The single caution rides on people, and it hangs on where the cress grew rather than the plant itself.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Watercress is no threat to cats. A curious nibble does zero harm, though most cats breeze right past the peppery leaves.
Dogs None
It is safe for dogs, leaves and stems alike. A dog that wolfs down a big mouthful might pick up a little harmless gas, but nothing worse.
Horses None
Horses can graze it without a worry. The sharp mustard tang usually keeps them from eating much of it anyway.
Rabbits Safe
Rabbits can tuck into watercress as part of a mixed green diet. Bring it in slowly, like any new leafy vegetable, so their gut adjusts.
Livestock Safe
Cattle, goats, and sheep can browse watercress safely. It packs no toxin that would harm grazing stock.
Birds Safe
Backyard hens and other birds peck at the tender leaves with no ill effect, and the greens toss a little variety into their feed.
People Safe
Watercress is a nutritious salad green, eaten raw or cooked. The one real catch is 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 watercress you grow is the plain wild species, but a couple of named types are worth chasing down.
Improved Broad Leaved
A cultivated strain bred for bigger, broader leaves and a heavier harvest than the wild plant kicks out.
Nasturtium microphyllum (one-row, small-leaved watercress)
A close cousin sporting smaller leaves and single-rowed seeds, and it crosses freely with true watercress wherever the two grow side by side.
How to propagate
Watercress takes off with barely any effort, whether you root a handful of cuttings in a glass of water or scatter seed across damp ground.
Stem cuttingsEasy
Any time during active growth, best in spring or fall · 1 to 2 weeks
Cuttings get you growing fastest, and you can take them any time the plant is active, with spring and fall firing best. Cut stems about 4 to 6 inches (10 to 15 cm) long and stand them in a glass of water or push them into wet soil. They root at the nodes within 1 to 2 weeks and away they go.
SeedEasy
Spring, in cool moist conditions · 2 to 3 weeks to germinate and establish
Seed jumps to life in the cool, damp weather 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 take hold.
Myths
Wild watercress is always safe to eat raw straight from the stream.
Cress yanked from water grazed by livestock can carry liver fluke larvae and other waterborne bugs you never see. Play it smart and cook wild-harvested cress, or grow your own in clean water, before eating any of it raw.
Edible watercress is the same plant as the ornamental garden nasturtium.
They share a peppery taste and a common name, and that is the whole overlap. Edible watercress is Nasturtium officinale in the mustard family, while the climbing garden nasturtium is Tropaeolum majus, a separate genus entirely.
Watercress needs deep running water and cannot be grown at home.
Flowing spring water is the dream setup, but it is nowhere near a must. A pot of rich soil standing in a tray of water, kept wet and refreshed, cranks out a steady supply right on a windowsill or patio.