Aquatic plant forming colonies that spread by underwater horizontal stems (rhizomes). Stems are round, often branched and jointed. Leaves are often underwater but may float. Whorls of tiny greenish flowers grow on spikes under or above the water.
Leaf margins smooth; floating leaves may be absent, if present wedge-shaped and taper towards stems; submersed leaves flat, narrow to round, not stemmed, 7 to 19 veins; stems round; fruits compressed, greenish-brown, grayish-green to olive-green.
Habitat
Found in the quiet waters of streams, lakes and ponds as well as in slow to moderately fast moving rivers in water up to 15 feet deep. Often found in calcareous waters (hard or alkaline waters higher in dissolved minerals especially calcium).
Flower Characteristics
Flower stalk is a thick, fleshy, cylindrical spike 1 to 3 inches long growing underwater or above the water surface. Tiny greenish flowers are crowded in whorls of 8 to 15 along the length of the spike. Each flower has 4 leaf-like sepals and no petals.
Leaf and Stem Characteristics
Floating and submersed (underwater) leaves are produced but floating leaves may be absent. Submersed leaves are reddish-brown, flat, narrow to round, may have wavy or smooth edges and a prominent midvein. Floating leaves are green, firm and wedge-shaped.
Fruit and Seed Characteristics
Fleshy fruit (drupe) 1/4 inch long has an egg-like, slightly flattened shape. It has 1 narrow ridge (keel) on its back edge and a pair of keels on its sides. A pointed projection (beak) about 1/16 inch at its tip is either upright or curves backwards.
1 seed is produced in a hard shell. The fruit does not split open at maturity to release the seed.