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Hydrilla verticillata

Hydrilla has whorls of tiny toothed leaves along long, freely branching stems.
Hydrilla has whorls of tiny toothed leaves along long, freely branching stems.

Hydrilla is a bay grass with whorls of tiny, toothed leaves along long, freely branching stems. It grows in freshwater portions of the Chesapeake Bay and most of its tributaries.


  • Long, freely branching stems
  • Tiny, straight or lance-shaped leaves that usually have visible teeth along the edges
  • Leaves grow in whorls of 4-5 along each stem
  • Tiny, white flowers in late summer
  • Rhizomes grow along or just below bottom sediments
  • Roots and small, fleshy tubers grow from the rhizomes


  • Grows in fresh waters, but has also been found in brackish waters
  • Does not need as much light as other bay grasses, so it can grow in more turbid areas


  • Common in the upper Chesapeake Bay and in most freshwater tributaries
  • Native to Africa, Australia and parts of Asia


  • Migratory waterfowl

Reproduction and Life Cycle:

  • Asexual reproduction takes place when plant fragments, tubers, roots and turions develop into new plants
  • Sexual reproduction occurs in late summer, when pollen from male flowers fertilizes female flowers. The seeds that form have about a 50 percent chance of growing into new plants.

Other Facts:

  • Introduced to the U.S. in the 1960s through the aquarium trade
  • First detected in the Potomac River near Washington, D.C., in 1982. By 1992, it covered 3,000 acres of the river.
  • Considered by some to be a nuisance because it can block boating channels and limit water sports
  • Has become an excellent habitat for fishes, particularly largemouth bass
  • Can be confused with common waterweed. You can distinguish hydrilla by its whorls of 4-5 leaves, the visible teeth along the edges of the leaves, and its fleshy tubers.

Sources and Additional Information:


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