Watercress

Nasturtium officinale

Watercress

Family: Brassicaceae


Weed class: monitor list
Native to: Asia, Europe and Northern Africa
Is this Weed Toxic?:

not known to be

Why Is It a Noxious Weed?

This plant is on the monitor list. Please contact its sponsor Cathy Lucero to report locations or for more information.

How would I identify it?

General Description

Emergent, perennial herbaceous plant growing in wet environments-with the ends of stems and leaves typically held above the water's surface.

Flower Description

Small white flowers are clustered at stem tips in flat-topped racemes. Flowers are on short stalks (pedicles), have 4 white to purplish veined and tinged petals and 6 stamens. Flowers bloom above water.

Leaf description

Older leaves are compound with 3-11 leaflets, having smooth or wavy margins, oval to lance-shaped and with the terminal leaflet being the biggest. Young leaves are simple (not compound).

Stem description

Usually observed growing as a tangle mass, stems are succulent and limp, except for tips which grow upright. Stems are often floating, growing to 2 feet (60 cm) long and can freely root at the lower nodes.

Fruit Seed Description

Flowers form thin, slightly curved, cylincrical pods (called siliques) that are 0.4-1 inches (10-25 mm) long, on stalks 0.3-0.5 inches (8-12 mm) long. Seeds are round and arranged in four rows inside the pod.

Where does it grow?

Watercress can be found growing in flowing streams and other shallow freshwater habitats, preferring cold, slow-moving water. Also can be found in mud along pond, stream and marsh edges. It can commonly be found in highway ditches. Herbarium records of watercress have been collected in eastern and western Washington.

How Does it Reproduce?

Plants spread by seed and vegetatively by stems and stem fragments that root at the nodes.

For More Information

WTU image database on Nasturtium officinale

Flora of North America treatment of Nasturtium officinale

Invasive.org webpage on Nasturtium officinale

Additional Photos