Rorippa aquatica (Eaton) E. J. Palmer & Steyerm.
Common Name: LAKE CRESS
Synonym: Armoracia aquatica
Coefficient of Conservatism: 8
Coefficient of Wetness: -5
Wetness Index: OBL
Physiognomy: Nt P-Forb
Status: T
Rorippa aquatica L. Mellichamp

Armoracia aquatica of Michigan Flora

Rivers and lakes, especially in cold spring-fed waters.

A remarkable aquatic plant, rarely seen except by those who know where to seek it or who recognize vegetative drifting fragments. The dissected submersed leaves fall off readily when mature; it is a unique experience to attempt to remove a nice-looking specimen of this species from the water and have the surface film strip off all the leaves as the stem is lifted! These leaves serve to propagate the plant vegetatively, growing leaves and roots for new plants from their base. The plant can also regenerate from stem fragments. The alternate leaves will readily distinguish this species from Ceratophyllum, Bidens beckii, and our common species of Myriophyllum; the presence of a central axis will distinguish the leaves from those of aquatic Ranunculus and Utricularia. Proserpinaca and some rare species of Myriophyllum have alternate leaves with a central axis, but in these the lateral segments of the leaf are not again divided, as they are in Rorippa aquatica.

Locations

Alger County
Alpena County
Cheboygan County
Gratiot County
Ionia County
Iosco County
Kent County
Keweenaw County
    Only on Isle Royale
Luce County
Mackinac County
Macomb County
Marquette County
Mason County
Muskegon County
Presque Isle County

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 11, 2017. http://michiganflora.net/species.aspx?id=606.