Elodea canadensis is a submerged, rooted or drifting perennial, aquatic, usually in dense beds, dioecious, leafy stems to 1 m long, dichotomously branched, fragile, easily fragmented, roots slender, unbranched, from nodes along stems.
Leaves opposite on lower stem, egg-shaped, small, upper leaves in whorls of 3, 0.6-1.7 cm long, 0.1-0.5 cm wide, linear, margin finely toothed, bright green, closely overlapping toward top of stem, dormant overwintering apices, with densely crowded, stiff leaves, develop in late summer, remain dormant in sediments until spring.
Flowers white, petals to 0.4 cm; elevated to water surface on a thin, elongate stalk to 30 cm long, flower and seed formation rarely occur.
Fruit dry, a beaked capsule ca 1 cm long including beak.
Wetland status: OBL.
Frequency in NYC: Very infrequent (or not inventoried).
Habitat: Quiet, neutral to alkaline water.
Notes: Winter dormancy broken by several days of temperatures above 18º C. Invasion tends to cause water quality changes including increased pH and fluctuations in phosphorus levels. Dispersal mostly by vegetative fragments. Eaten by waterfowl and various insects. Provides cover for small fish and aquatic invertebrates, these, in turn, help control mosquito populations in artificial ponds (Spicer and Catling 1988). Prefers cool (under 25º C), nutrient rich water, 1-8 m deep, pH 6.6-10. Increases dissolved oxygen. Tolerates light levels from 15% of full sun to full sun. Apparently attacked by relatively few insects and diseases (Spicer and Catling 1988).