Common name: Elodea, Canadian Pondweed, American Elodea, American Waterweed, Canadian Elodea, Canadian Waterweed, Oxygen Weed, American Duckweed
Elodea canadensis Michx. APNI* Synonyms: Anacharis canadensis (Michx.) Planch. APNI*
Description: Attached dioecious submerged aquatic perennial; branched stems to 3 (-6) m long with crowded internodes near the apex and producing long thread-like, often reddish, roots at the lower nodes.
Leaves in whorls of 3 or rarely 4 or 5, curled, 5–20 mm long, (1-) 2–5 mm wide, margins minutely toothed or entire.
Flowers arising from the upper leaf axils. Female flowers with spathe evenly 2 toothed at apex; hypanthium usually 20–150 mm long, sometimes longer, not recorded for N.S.W. Male flowers with spathe 10–20 mm long, evenly 2 cleft at apex; hypanthium usually breaking off to allow the upper portion of the flower to float to the surface; outer perianth segments 3.5–5 mm long, inner segments c. 5 mm long; stamens 9.
Flowering: during warmer months.
Distribution and occurrence: Grows in deep, cold, flowing or stationary water; a major weed of larger irrigation supply channels. Native of North America.
NSW subdivisions: *NC, *CC, *SC, *ST, *CWS, *SWS, *SWP
Other Australian states: *Vic. *Tas. *W.A. *S.A. *Qld
Differs from the related species Egeria densa Dense Waterweed and Hydrilla verticillata Hydrilla by having fewer leaves in a whorl and shorter individual leaves, with these other species both having leaves up to 40 mm long in whorls of 3-8. In Australia, where fruits have not been found, reproduction and spread is by rooted fragments. For further information see Weeds in Australia profile compiled by P.G. Kodela (2008).
Text by S. W. L. Jacobs; revised by P.G. Kodela (July 2012)
Taxon concept: Flora of NSW 4 (1993)
APNI* Provides a link to the Australian Plant Name Index (hosted by the Australian National Botanic Gardens) for comprehensive bibliographic data
***The AVH map option provides a detailed interactive Australia wide distribution map drawn from collections held by all major Australian herbaria participating in the Australian Virtual Herbarium project.
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