General Information
Species Name: Myriophyllum spicatum
Also Known As: spike watermilfoil
Family: Haloragaceae (Water Milfoil)
Growth Form: Forb (submersed aquatic)
Life Span: Perennial
Flowering Dates: June-July
Origin: Europe, Asia, North Africa
Noxious: No
Category 2: Priority Aquatic Invasive Species
Why Is It Invasive?
Once introduced into a waterbody, Eurasian watermilfoil grows densely, crowding out native vegetation and prohibiting boater and angler access. With growth too dense to be suitable habitat for native fish species, Eurasian watermilfoil overcrowds space for suitable habitat to grow. Eurasian watermilfoil can hybridize with its native cousin, northern watermilfoil, and become resistant to most chemical treatments, requiring costlier treatment methods.
What Does It Look Like?
General Characteristics
Eurasian watermilfoil is a rooted, submerged aquatic plant. Roots are thin, white, and sometimes form dense clumps underneath the plant. Eurasian watermilfoil can grow to over 2 meters high and is limp when removed from the water.
Eurasian watermilfoil looks very similar to its native cousin, northern watermilfoil. Unlike Eurasian watermilfoil, northern watermilfoil has only 5-12 leaflets per leaf and remains stiff when removed from the water. Northern watermilfoil’s stem is a lime green. Hybrid milfoil may possess characteristics of both plants or resemble on Eurasian watermilfoil, requiring genetic testing to confirm its genetic makeup.
Flowers
A small pink flower spike up to four inches long produces tiny yellow flowers. Male and female flowers are found on the same plant. The female flowers are basal while the male flowers are located distally. The female flowers have a 4-lobed pistil and lack sepals and petals. The male flowers have 4 pink petals and 8 stamens.
Leaves
Leaves are bright green, finely dissected, and whorled (radiating out from a single point) around the stem with more than 14 leaflets per leaf. Space between whorls along the stem can be a half inch or greater. The delicate leaflets give this plant a feathery appearance.
Stems
The plants are rooted and the slender, reddish-green stems grow up to the water surface, usually reaching 3-10 ft. (0.9-3 m) in length and can be as much as 30 ft. (9.1 m) long. Tips of the plant are sometimes red or pink in color.
Seeds
The very small globular fruit of Eurasian watermilfoil are indehiscent, and contain 4 seeds. Even though each plant can produce approximately 100 seeds per season, this species is more successful at reproducing via fragments.
Photos
Where Does It Grow?
Eurasian watermilfoil requires stagnant to slowly moving water and can tolerate brackish conditions. Eurasian watermilfoil is usually found in waters 1-4 meters deep and is successful in varying sediment types, preferring finely textured sediments. Growth is best facilitated in low light and high water temperature conditions.
How Does It Spread?
Eurasian watermilfoil is spread through fragmentation of plants, the release of aquarium plants and pets, and the transportation of recreational boats, fishing equipment, and any other equipment that can come in contact with this invasive plant. The plant can spread when fragments are attached to equipment and transported to another body of water.
How Do I Control It?
Management of invasive aquatic plants involving either mechanical removal of plants or application of herbicides to public waters requires a permit. Contact the Contact the Nebraska Game and Parks Commission for more information.
Mechanical
Cutting or pulling the plant by hand or with equipment such as rakes or cutting blades could break it into fragments, allowing it to further spread. Contact the Nebraska Game and Parks Commission to determine appropriate removal methods.
Cultural
CLEAN your watercraft, trailer, angling gear and other equipment. Remove all aquatic vegetation and animal species from your equipment.
DRAIN your watercraft at the ramp by removing the boat plug and draining all live wells and ballast tanks.
DRY your watercraft, trailer and other equipment for at least 7 days before visiting another waterbody. If coming from a known zebra mussel infested waterbody, allow your watercraft and equipment to dry for at least 30 days before using them on an un-infested waterbody.
DON'T LET IT LOOSE. Do not release or transport exotic or non-native fish species to new ecosystems, and do not dump aquariums. It is unlawful to release any aquatic species into a waterbody other than the one from which it was harvested. Doing so can promote the spread of AIS.
Chemical
Application of chemicals to public waters requires a permit. Contact the Contact the Nebraska Game and Parks Commission for more information.
What Should I Do If I See It in Nebraska?
If you see Eurasian watermilfoil in Nebraska, you should report it to the Nebraska Game and Parks Commission's Aquatic Invasive Species (AIS) Program using their AIS Report Form. For guidance on what information to include in your report, check out our reporting tips.
References and More Information
Center for Aquatic and Invasive Plants
Center for Invasive Species and Ecosystem Health
Lady Bird Johnson Wildflower Center
Long Island Invasive Species Management Area
Minnesota Department of Natural Resources
National Invasive Species Information Center
Nebraska Game and Parks Commission
USGS Nonindigenous Aquatic Species