PO Box 419

Hotchkiss, CO 81419



fax: 720-880-3051




Hydrilla verticillata (L. f.) Royle


Keys to Identification

  • Hydrilla is an aquatic weed that has the potential of impacting our waterways and agricultural water supplies. Hydrilla has not yet been found in Colorado.

Family: Tape grass (Hydrocharitaceae)


Other Names: waterthyme, Florida elodea




Legal Status: Colorado Noxious Weed List A


New in Colorado – call your county weed supervisor if you find this plant!


photo courtesy of USDA APHIS


Lifecycle: Perennial aquatic


Growth form: Forb/herb


Flower: Female flowers tiny and white, with 6 petals. Male flowers tiny greenish, closely attached to the leaf axle


Seeds/Fruit: Yellowish turions ("potato-like" tubers). Can remain viable for 4 years.


Leaves: Leaves are small, pointed and arraigned in whorls of 4-8 along the stem. Leaf margins are distinctly saw toothed.


Stems: Submersed stems are long and slender that branch profusely at the water surface. Stem fragments are one means of reproduction


Roots: Roots in the hydro soil, adventurous roots are white.


Other: This plant is noticeable rough when pulled through the hand. Southern populations (US) overwinter as perennials; northern populations overwinter and regrow from tubers.



Similar Species

Exotics: Egaria densa


Natives: Elodea canadensis



Agricultural: Could severely impact the Colorado’s system of water delivery (irrigation ditches and canals).


Ecological: Can grow in natural water bodies displacing native plants.


Other: In the South hydrilla impacts the recreational use of water bodies for boating, fishing and swimming. Major infestations limit sport fish size and weight.


Habitat and Distribution

General requirements: Aquatic plant. In Russia hydrilla grows as far north as 50° N Latitude (the equivalent of the USA/Canadian Border)


Distribution: Arizona, Atlantic Coast States to Connecticut (Excluding; New Jersey and New York), California, Gulf Coast States and Tennessee. No infestations of this plant have been documented in Colorado.


Historical: Dioecious type native to India, monoecious plants native to Korea. Believed to have been brought to Florida in the 1950’s for use as an aquarium plant.


Biology/ Ecology

Life cycle: Perennial


Mode of reproduction: Mainly plant fragments and turions (vegetative structures)


Seed production: Minimal


Seed bank: Unknown


Dispersal: Water movement, animals, man, recreation, equipment





Aquatic, Wetland and Invasive Plant
Particulars and Photographs
University of Florida, Center for Aquatic and Invasive Plants

Non-Native Invasive Aquatic Plants in the United States
Center for Aquatic and Invasive Plants, University of Florida and Sea Grant



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