Nasturtium officinale (Watercress)
|Also known as:||Small-leaved Water-cress|
|Habitat:||part shade, sun; cool flowing streams and springs|
|Bloom season:||April - July|
|Plant height:||4 to 15 inches|
|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 ¼ to 3/8 inch across with 4 rounded white petals, 6 yellowish stamens, a short central style, and a purplish green ovary.
Leaves and stems:
Leaves are 2 to 4 inches long, ¾ to 1½ inches wide, compound in groups of 3 to 9. Leaflets are oval to lance-shaped with irregular edging, typically rounded at both ends, the terminal leaflet rather larger than the rest and may be nearly round in shape. Stems and leaves are hairless. Stems float on the surface of the water or spraw across mud, rooting freely at the nodes.
Fruit is a slender pod, ½ to 1¼ inches long with a short abrupt beak, straight to slightly curved, spreading to somewhat ascending. Seeds are oval, reddish brown, 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 seeds 1 row, and is aptly commonly called One-row Yellowcress.
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Photos by K. Chayka taken at Whitewater Wildlife Management Area. Photos courtesy Peter M. Dziuk taken in Dakota, Winona and Washington counties.
Have you seen this plant in Minnesota, or have any other comments about it?