Description:Hydrilla verticillata is a member of the Hydrocharitaceae family. It closely resembles other members of this family such as Elodea canadensis and Egeria densa. Several members of this family are popular with the aquarium and nursery industry because they are hardy, tolerant plants. Consequently, some have become severe pest problems where introduced to waters outside their native range.
History:Hydrilla was first introduced into North America in the mid to late fifties by the aquarium trade. California officials have also traced hydrilla infestations to shipments of mail order waterlilies. Once introduced and established, hydrilla is easily spread through boating and fishing activities and by waterfowl. Hydrilla tubers are readily consumed and regurgitated tubers have been shown to be viable.
Biology & Spread:Commonly reproduces from fragmented stems which readily regrow, forming new clones of the original plant. New shoots also bud from leaf axils (where petioles attach to the stem) as well as from subterranean tubers. Hydrilla can grow up to 1 inch in a day and stems can reach 30 feet in length. Stems grow until they reach the water surface, filling the entire water column.
Ecological Threat:Dense underwater stands of hydrilla raise water pH and temperature, and lower dissolved oxygen. While the number of fish is often increased, large fish become more rare. Promotes mosquito habitat. Potentially affects power generation by clogging dams
US Habitat:
Hydrilla is a submersed, freshwater perennial herb, generally rooted on the bottom in depths of greater to 20 feet where water clarity is good. It is found in lakes, rivers, reservoirs, ponds, and ditches. It tends to form monospecific stands that can cover hundreds of acres.
Distribution
US Nativity:
Introduced to U.S.
Native Origin:
Europe; Old World (Bailey, L.H. and E.Z. Bailey, Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada, MacMillan Publishing Co., Inc., New York , (1977).); NatureServe Explorer
US States:
AL, AZ, CA, CT, DE, FL, GA, LA, MD, MS, NC, SC, TN, TX, VA, WA
EDDMapS: View Texas Map from Early Detection & Distribution Mapping System for
Hydrilla verticillata
Other Texas alternatives include White water lily (Nymphaea odorata), Delta arrowhead (Sagittaria platyphylla), Floating bladderwort (Utricularia radiata).
Management:Scientific research and 30 years of practical experience by aquatic plant managers using herbicides, biological agents, mechanical removal, and physical habitat manipulation have produced relatively successful management programs in Florida and other states. However, in spite of long-term intensive management efforts, hydrilla is still a major weed problem in the states where it has become well established.
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Listing Source
Texas Department ofAgriculture Noxious Plant List
Texas Parks and Wildlife Department Prohibited Exotic Species
Invaders Program
Federal Noxious Weed
Union of Concerned Scientists
United States Forest Service Southern Research Station
