Hydrilla
Hydrilla verticillata
Hydrilla leaves come in whorls of five, though some may have four. The leaves have teeth that are easily visible. (Photo by Matt Rath/Chesapeake Bay Program) USAGE REQUEST INFORMATION The Chesapeake Bay Program's photographic archive is available for media and non-commercial use at no charge. To request permission, send an email briefly describing the proposed use to requests@chesapeakebay.net. Please do not attach jpegs. Instead, reference the corresponding Flickr URL of the image. A photo credit mentioning the Chesapeake Bay Program is mandatory. The photograph may not be manipulated in any way or used in any way that suggests approval or endorsement of the Chesapeake Bay Program. Requestors should also respect the publicity rights of individuals photographed, and seek their consent if necessary.
Hydrilla leaves grow in whorls of 4-5. (Maryland Department of Natural Resources)
Hydrilla has freely branching stems with whorls of leaves. (Maryland Department of Natural Resources)
A scientist holds a mass of hydrilla. (Maryland Department of Natural Resources)
Hydrilla leaves have visible teeth. (Darkmax/Wikimedia Commons)
Hydrilla is a nonnative underwater grass that grows in freshwater portions of the Chesapeake Bay and most of its tributaries.
Appearance
Hydrilla is made up of long, freely branching stems with tiny, straight or lance-shaped leaves that usually have visible teeth along the edges. Leaves grow in whorls of four or five along each stem. Tiny, white flowers appear in late summer. Rhizomes grow along or just below bottom sediments. Roots and small, fleshy tubers grow from the rhizomes.
Predators
Migratory waterfowl feed on hydrilla.
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% chance of growing into new plants.
Did You Know?
- Hydrilla was introduced to the U.S. in the 1960s through the aquarium trade. It was first detected in the Potomac River near Washington, D.C., in 1982. By 1992, it covered 3,000 acres of the river.
- It is considered by some to be a nuisance because it can block boating channels and limit water sports
- Hydrilla has become an excellent habitat for fishes, particularly largemouth bass
- It can be confused with common waterweed. You can distinguish hydrilla by its whorls of four to five leaves, the visible teeth along the edges of its leaves and its fleshy tubers.
Sources and Additional Information
- Underwater Grasses in Chesapeake Bay & Mid-Atlantic Coastal Waters by Maryland Sea Grant
- Life in the Chesapeake Bay by Alice Jane Lippson and Robert L. Lippson
- Chesapeake Bay: Nature of the Estuary, A Field Guide by Christopher P. White
- Bay Grass Key: Hydrilla – Maryland Department of Natural Resources
- Invasive Alien Plant Species of Virginia: Hydrilla – Virginia Department of Conservation and Recreation
- Plant Invaders of Mid-Atlantic Natural Areas: Hydrilla – U.S. Fish & Wildlife Service
- PLANTS Database: Hydrilla verticillata – USDA Natural Resources Conservation Service
Quick Facts
Species
Nonnative
-
Size
Stems can reach 25 feet in length
-
Habitat
Grows in fresh waters, but has been found in brackish waters. Does not need as much light as other bay grasses, so it can grow in more turbid areas.
-
Range
Common in the upper Chesapeake Bay and in most freshwater tributaries. Native to Africa, Australia and parts of Asia.
-
Status
Stable