CWMA

PO Box 364

Paonia, CO 81428

 

970-361-8262

fax: 720-880-3051


Email:contact@cwma.org

 

 

Hydrilla

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

 

USDA Code: HYVE3

 

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


Identification

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

 


Impacts

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

 

 

 

References

Aquatic, Wetland and Invasive Plant
Particulars and Photographs
University of Florida, Center for Aquatic and Invasive Plants
http://aquat1.ifas.ufl.edu/hyvepic.html

Non-Native Invasive Aquatic Plants in the United States
Center for Aquatic and Invasive Plants, University of Florida and Sea Grant
http://plants.ifas.ufl.edu/seagrant/hydver2.html

 

 

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