Variable Pondweed (Potamogeton gramineus)

Variable Pondweed (Potamogeton gramineus)

The Variable Pondweed (Potamogeton gramineus); also known as Variable-leaf Pondweed, Variable-leaved Pondweed and Grass-leaved Pondweed; is one of the most common submerged plants in French Hill Pond. It is a perennial, forb/herb in the Pondweed Family (Potamogetonaceae) and order, Najadales. The family and genus names are from the Greek for "neighbor of a river." The species name comes from the Latin for "grassy." The order name is from the Greek and Latin verb "to swim." As a noun, the order name refers to a water nymph.

This plant has two kinds of leaves. The submerged leaves are alternate and linear with three to seven veins running lengthwise. They are up to 3 inches (8 centimeters) long and 0.4 inches (1 centimeter) wide. The floating leaves are elliptical, up to 2 inches (5 centimeters) long and one inch (2.54 centimeters) wide. These floating leaves occur singularly or in pairs. The photographs on this page were taken on French Hill Pond late in the season. Therefore, the leaves appear browner than normal. The submerged leaves are naturally translucent and appear browner because of the turbidity of the water in French Hill Pond.

The flowers are clustered in cylindrical spikes extending to about an inch (3 centimeters) long above and below the water. The following photograph shows these spikes among the floating leaves. The dry seeds are oval with a ridge along part of the rim and have a protrusion at one end called a "beak."

 

Variable Pondweed (Potamogeton gramineus) Flower

The following photograph shows the size of the leaf and flowers. The size of the leaves can vary greatly.

Leaf and Flower

The following 400X microphotograph shows the stomata of a Variable Pondweed floating leaf. The cells are arranged in thin, interspersed layers allowing light to irradiate each cell.

Variable Pondweed Floating Leaf 400x

The submerged leaves of immature plants are shown in the following photograph. These immature plants are easily confused with immature versions of similar species in the same genus.

Variable Pondweed (Potamogeton gramineus) Submerged

The Variable Pondweed (Potamogeton gramineus) has a rhizomic root system and can spread rapidly in shallow water with a bottom consisting of firm sediment. In addition to propagation by seed and rhizomes, this plant will develop winter buds towards the end of the season called "turions" that behave much like seeds. Waterfowl and mammals like deer will eat this plant.

 

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