USGS - science for a changing world

Northern Prairie Wildlife Research Center

  Home About NPWRC Our Science Staff Employment Contacts Common Questions About the Site

Aquatic and Wetland Vascular Plants of the Northern Great Plains

Elodea Michx. -- Waterweed

Stems slender, lax to rather rigid and brittle, sparingly to freely branched, rooting from the lower nodes or sometimes free-floating. Leaves sessile, crowded toward the apex, mostly in whorls of 3(4) or opposite and decussate, the margins finely serrulate. Flowers minute, delicate, often lost in collection, solitary in the upper leaf axils, subtended by a 2-lobed spathe, usually extended to the water surface by a long, threadlike hypanthium or (in male flowers of E. nuttallii) sessile and breaking free to float to the surface; sepals 3; petals 3 or seldom absent; male flowers containing 9 stamens; female flowers with 3 staminodes and 3 stigma lobes protruding at the summit of the hypanthium, the stigmas entire or 2-lobed. Fruit ovoid to cylindric, several-seeded.


St. John, H.  1965.  Monograph of the genus Elodea.  Part 4:  The 	
     species of the eastern and central North America.  Rhodora 67:1-35, 

Lead Characteristic Go To
1 Middle and upper leaves in whorls of 3(4). Lead 2
1 Middle and upper leaves decussate. E. longivaginata
2 Leaves mostly (1)1.5-3(5) mm wide, obtuse-apiculate at the apex; male flowers extended to the surface by a long, threadlike hypanthium; sepals of female flowers 2-3 mm long. E. canadensis
2 Leaves (0.3)0.7-1.5 mm wide, acute or acute-apiculate at the apex; male flowers sessile inside the spathe, breaking free to float to the surface at anthesis; sepals of female flowers ca. 1 mm long. E. nuttallii

52. Hydrocharitaceae, the Frog's-bit Family
1. Elodea Michx. -- Waterweed
1. Elodea canadensis L. C. Rich. in Michx.
2. Elodea longivaginata St. John
3. Elodea nuttallii (Planch.) St. John

Return to Family -- Hydrocharitaceae - The Frog's-bit Family
Return to Contents

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Webmaster
Page Last Modified: Saturday, 02-Feb-2013 06:38:07 EST
Sioux Falls, SD [sdww54]