Hydrilla

Hydrilla verticillata

Description

Perennial aquatic plant that grows rooted to the bottom with long stems that reach the water's surface. Leaves occur in whorls of three to five, and have sharp spines along their margins, giving a toothed appearance. A characteristic that distinguishes hydrilla from similar family members are the small, auxillary leaf scales that are found next to the stem and inserted at the base of the leaf. Commonly confused with the Washington native species Elodea Canadensis.

Habitat

Freshwater; lakes, rivers, reservoirs, ponds, ditches

Distribution

King County, WA

Impacts

Makes for poor habitat for native fish and other wildlife by increasing water's pH, decreasing oxygen, and increasing temperature; creates breeding ground for mosquitoes; interferes with recreational activities and clogs irrigation ditches and intake pipes

Dispersal Methods

Underground rhizomes, above ground stolons, and tuber and turion production

Listings

ODA A list and OISC 100 Most Dangerous Invaders

Factsheets

Washington State Noxious Weed Control Board Fact Sheet on Giant Knotweed

Photos

http://www.forestryimages.org/search/action.cfm?q=hydrilla

Distribution Map

http://plants.usda.gov/java/county?state_name=Washington&statefips=53&symbol=HYVE3

CWMA Warnings

Columbia Gorge

North Coast

Mid-Coast

Mid-Willamette