General Information
Species Name: Nasturtium officinale
Also Known As: European watercress, nasturium, small-leaved watercress, two-rowed watercress, watercress, water-cress, yellowcress
Family: Brassicaceae (Mustard)
Growth Form: Forb (emergent aquatic)
Life Span: Perennial
Flowering Dates: April-July
Origin: Eurasia, Asia, Northern Africa
Noxious: No
Category 3: Established Aquatic Invasive Species
Why Is It Invasive?
Common watercress is a widespread and problematic invasive of clear streams, springs, and brooks that can rapidly spread out and form dense stands on the surface of the water, choking out natives.
What Does It Look Like?
General Characteristics
Common watercress is erect or spreading and can grow 4-18 inches tall. It floats or lies in water or mud and forms large, tangled wintergreen masses. It often forms dense stands in spring runs.
Flowers
It produces small white and green stalked flowers in clusters at the ends of the shoots. Each flower has 4 white or pink tiny, rounded petals that are yellowish at the base and up to 1/4 inch wide. They may have tinges of blue or purple.
Leaves
The leaves are dark green, narrow, smooth, wavy, and up to 6 inches long. They are alternate (there is one leaf per node along the stem), compound (made up of two or more discrete leaflets), and simple (i.e., lobed or unlobed but not separated into leaflets). The leaf on the end of each stem is longer and broader than the leaves on the sides of each stem.
Stems
Watercress has hairless, hollow, spreading stems that are grooved, succulent, angled, and float on water, growing to a height of 1-2 feet. The stems frequently fall over and root at nodes.
Seeds
Young seed pods (siliques) can be almost a centimeter long. The seeds have a sharp, peppery smell. The fruit is narrow, green, and with a slightly curved and erect seed pod.
Photos
Where Does It Grow?
Common watercress grows in flowing streams, ditches, lake margins, swamps, marshes, and/or seeps. Watercress prefers to take roots in limey, gravelly sediment and is intolerant of heavy shade.
How Does It Spread?
Common watercress was intentionally introduced by green industry and cultivation. It is one of the oldest known leaf vegetables consumed by humans. Fragments are dispersed unintentionally by wind, water, and animals.
How Do I Control It?
Management of invasive aquatic plants involving either mechanical removal of plants or application of herbicides to public waters requires a permit. Contact the Contact the Nebraska Game and Parks Commission for more information.
Mechanical
Cutting or pulling the plant by hand or with equipment such as rakes or cutting blades could break it into fragments, allowing it to further spread. Contact the Nebraska Game and Parks Commission to determine appropriate removal methods.
Cultural
CLEAN your watercraft, trailer, angling gear and other equipment. Remove all aquatic vegetation and animal species from your equipment.
DRAIN your watercraft at the ramp by removing the boat plug and draining all live wells and ballast tanks.
DRY your watercraft, trailer and other equipment for at least 7 days before visiting another waterbody. If coming from a known zebra mussel infested waterbody, allow your watercraft and equipment to dry for at least 30 days before using them on an un-infested waterbody.
DON'T LET IT LOOSE. Do not release or transport exotic or non-native fish species to new ecosystems, and do not dump aquariums. It is unlawful to release any aquatic species into a waterbody other than the one from which it was harvested. Doing so can promote the spread of AIS.
Chemical
Application of chemicals to public waters requires a permit. Contact the Contact the Nebraska Game and Parks Commission for more information.
What Should I Do If I See It in Nebraska?
If you see common watercress in Nebraska, you should report it to the Nebraska Game and Parks Commission's Aquatic Invasive Species (AIS) Program using their AIS Report Form. For guidance on what information to include in your report, check out our reporting tips.
References and More Information
Center for Invasive Species and Ecosystem Health
Midwest Invasive Species Information Network
Nebraska Game and Parks Commission
North Carolina Botanical Garden
USGS Nonindigenous Aquatic Species
U.S. Fish and Wildlife Service