Nasturtium officinale (Watercress)
|Also known as:||Small-leaved Water-cress|
|Habitat:||part shade, sun; cool, shallow water, muddy banks, streams, springs, seeps, wet ditches, ponds|
|Bloom season:||April - July|
|Plant height:||4 to 15 inches|
|Wetland Indicator Status:||GP: OBL MW: OBL NCNE: OBL|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Elongating racemes at the ends of many branching stems, with blooming flowers clustered at the tip. Flowers are about ¼ inch (to 6 mm) across with 4 rounded white petals, 6 yellowish stamens, a short central style, and a purplish green ovary.
Leaves and stems:
Leaves are 1 to 6+ inches (to 15+ cm) long, ¾ to 1½ inches wide, compound with 3 to 9 leaflets, occasionally more. Leaflets are lance-elliptic to narrowly egg-shaped with somewhat irregular edging, typically rounded at both ends, the terminal leaflet rather larger than the rest and may be nearly round in shape, though leaflets can elongate, becoming more narrowly lance-oblong. Stems and leaves are hairless. Stems may be erect, reaching a height of 3 feet or more, but more typically float on the surface of the water or sprawl across mud, rooting freely at the nodes and forming dense mats.
Fruit is a slender pod, 3/8 to 1 inch (1 to 2.5 cm) long, slightly curved, spreading to somewhat ascending, and have a short, abrupt beak at the tip. Seeds are oval, reddish brown when mature, and arranged in 2 rows.
Formerly known as Rorippa nasturtium-aquaticum, this is the same Watercress found in your local grocer's produce department. A widespread and problematic invasive of clear streams, springs and brooks, it can rapidly spread out on the surface of the water, choking out natives. The stems and leaves are crisp and can be used as a salad with a pungent radish flavor. I do like harvesting it wild, but cleaning off aquatic insects and spiders is a chore as well as running the risk of beaver-fever (girhardia), or ingesting the toxins in our polluted waters. When not fruiting it is virtually indistinguishable from Nasturtium microphyllum (Rorippa microphylla), also found in Minnesota. N. microphyllum has pods that are generally longer and more slender, containing seeds in 1 row, and is aptly commonly called One-row Watercress.
Like many weeds, Watercress is much more widespread in Minnesota than herbarium records indicate; there are currently over 130 reports in MN on the national weed tracking system EDDMapS.
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- Watercress plant
- erect Watercress plant with elongated leaflets
- a colony of Watercress
- Watercress in a floodplain
- Watercress in a flowing stream
- a dense infestation of Watercress and Forget-me-not, along the Mississippi River
- leaves in early spring
Photos by K. Chayka taken at Pine Bend SNA and Whitewater Wildlife Management Area. Photos by Peter M. Dziuk taken in Dakota, Winona and Washington counties.
Have you seen this plant in Minnesota, or have any other comments about it?