Eurasian watermilfoil

Eurasian watermilfoil Myriophyllum spicatum Code: Photo:

Eurasian watermilfoil (Myriophyllum spicatum) is a native of Europe and Asia and was once sold in this county as an aquarium plant. It is an underwater plant that has become a major problem in many of Washington's lakes, rivers, and streams.

Key Characteristics

• Count the pairs of leaflets. Eurasian watermilfoil generally has twelve or more pairs.
• The leaves of Eurasian watermilfoil tend to collapse around the stem when removed from the water--native species are generally more robust.
• Eurasian watermilfoil leaflets occur in whorls of four around the stem.

Eurasian watermilfoil (and other milfoil species) may be distinguished from other aquatic plants by their feather-like leaflets. However, there are also a number of native milfoil species in Washington. It's very difficult to tell the common native milfoil species from the foreign Eurasian watermilfoil, but there are some differences.

Because the native milfoils and Eurasian watermilfoil are so similar in appearance, even experts sometimes need to rely on DNA analysis to make a positive identification.

Distribution
Eurasian watermilfoil has become widely distributed within lakes and rivers in eastern and western Washington. It is found in Lake Washington, the Columbia River, the Pend Oreille River, the Snake River, the Okanogan River, and is in many other Washington lakes.

Parrotfeather milfoil

Parrotfeather milfoil Myriphylum aquaticum Code: Photo:

Parrotfeather milfoil (Myriophyllum aquaticum) is a South American native that has been commonly sold as an aquatic garden plant. It is spectacular in appearance with bright green "fir tree-like" vegetation sticking up to a foot above the surface of the water. The brownish underwater stems (rhizomes) are very tough and the underwater leaves are often decomposed and not present. Parrotfeather milfoil forms dense mats that extend out from the shoreline into deeper water. Parrotfeather milfoil mats form ideal breeding ground for mosquitoes, and water under the mats often is very acidic.

Key Characteristics

• Bright green, "fir tree-like" emergent leaves and stems.
• Leaflets arranged in whorls (4-6) around the stem with each leaflet having a feather-like pattern.
• Dense mat of intertwined brownish stems (rhizomes) in the water with abundant long roots.
• Reddish, feathery-leafed, very limp submersed leaves may be present.

Parrotfeather milfoil is easy to identify. Because it is a milfoil, the leaves are feather-like in appearance, but unlike the other Washington milfoils, this species has emergent stems and leaves. All Parrotfeather milfoil plants in Washington are female.

Distribution
Parrotfeather is limited in distribution and has not yet been reported from eastern Washington. It is found in the Chehalis River and at other locations in western Washington. Parrotfeather seems to prefer slowly-moving nutrient-rich waters. Once established, parrotfeather milfoil is extremely difficult to control.

Brazilian elodea

Brazilian elodea Egeria densa Code: Photo:

Brazilian elodea (Egeria densa) is a South American native, that until 1996, was sold in pet stores as the very popular aquarium plant, Anacharis. The characteristics that make Brazilian elodea a good aquarium plant (rapid growth under low light levels, easy propagation, and tolerance of a wide range of water and sediment types) also make it a nuisance aquatic plant, when it escapes and grows in lakes and streams. Brazilian elodea is a densely-leafed, bright green, robust underwater plant. It overwinters in an evergreen state and grows rapidly in the spring, forming a canopy of intertwined stems at the surface that shades out native aquatic plants. Brazilian elodea appears to outcompete Eurasian watermilfoil when the two species occur together and can be even more difficult to control than milfoil.

Key Characteristics

• Bright green underwater plant, sometimes with fragrant white (three-petaled) floating flowers.
• Leaves arranged in whorls of four to six.
• Leaves greater than one-half inch long and less than one-quarter inch wide.
• No tubers attached to the roots in sediment.

Brazilian elodea is relatively easy to identify, but it can be readily confused with its cousins, hydrilla and our commonly-occurring native American elodea. All Brazilian elodea plants in Washington are male and floating white male flowers are sometimes seen. (See also hydrilla description).

Distribution
Brazilian elodea has not been reported from eastern Washington, but occurs in a number of lakes in western Washington and is of serious concern. Local lake residents sometimes spend thousands of dollars each year for control.

Hydrilla

Hydrilla Hydrilla verticillata Code: Photo:

Hydrilla (Hydrilla verticillata) is considered the most troublesome plant in North America. It is native to Australia, Africa, and some parts of Asia. Hydrilla was introduced into the United States as an aquarium plant, but is no longer sold as such. Hydrilla has been known to "hitchhike" into uninfested waterbodies on the rhizomes of waterlilies offered for sale to water gardeners. Hydrilla forms dense, tangled mats of vegetation that inhibit the growth of native aquatic plants and interfere with recreation. It grows rapidly under very low light levels, in a variety of aquatic habitats, from still to flowing waters, and in depths of an inch to 50 feet.

Key Characteristics

• Small, potato-like tubers (one quarter to one half inch long) are attached to the roots.
• Spiny looking leaf edges (look closely).
• The mid-rib of the leaf is reddish.
• Leaves are arranged around the stem in whorls of three to 10.

We especially want people to monitor for hydrilla because it can cause major habitat and recreational losses. It is not well established in Washington and immediate action can eradicate it. Hydrilla can be difficult to identify because it so closely resembles American elodea and Brazilian elodea.

Distribution
Hydrilla distribution in Washington is very limited and we want to keep it that way! If you think you have found hydrilla, contact Kathy Hamel or Jenifer Parsons immediately.Its currently limited to the Pipe and Lucerne Lake System in King County where an eradication project is underway.

Fanwort

Fanwart Caboma caroliniana Code: Photo:

Fanwort (Caboma caroliniana) is a native of our North American east coast. This beautiful underwater plant has been cultivated and hybridized as an aquarium plant. It is still legally sold in Washington for aquarium use, but has "escaped" into western Washington and Oregon waters where it is thriving. Fanwort grows very densely and excludes native aquatic plant species. Even on the east coast, where it is native, fanwort is considered a serious aquatic nuisance.

Key Characteristics

• Pairs of fan-shaped underwater leaves arranged opposite each other with each fan-shaped leaf on one third inch long stalks.
• Small (less than one inch long), oval, floating leaves with the stem attached in the center (may not always be present).
• Slender stem is sometimes covered with a gelatinous slime.

Fanwort has distinctive, fan-shaped underwater leaves arranged in pairs along the stem. Fanwort can be bright green to reddish in color. In the water, fanwort has a "tubular" look because the leaves are quite dense on the stem and there is little branching. Small, floating leaves may also be present. Fanwort produces small white flowers with a yellow spot near the base.

There are two other fan-shaped leafed underwater plants in Washington that can be mistaken for fanwort. The aquatic buttercup has alternate rather than opposite leaves. The water marigold has opposite leaves on very short stalks and yellow, daisy-like flowers.

Distribution
Fanwort is known to be growing in only one location in western Washington in a slough off the Columbia River in the Longview/Kelso area.