Aquatic Invasive Species
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Aquatic Invasive Species
| Eurasian watermilfoil
Eurasian watermilfoil
(Myriophyllum spicatum)
Photo Credit: Alison Fox, University of Florida, Bugwood.org
Eurasian Watermilfoil is a submersed, perennial herb. It produces an extensive, shallow root system in
water sediment that is capable of generating new shoots. It grows stems and branches that are 1 to 20 feet long with the
average size from 6 to 8 feet. The branched stems produce four leaves at each node, but are leafless at the base. The
nearer stem grows to the water surface and the internodes branch and leaf development occurs.
Heavy infestations form impenetrable mats
of stems and leaves form below the water's surface. The stem tips are tassel-like and reddish
early in the season. The feather-like, pinnate leaves have 14 or more pairs of leaflets and are around 1-inch long.
White to pinkish flowers are produced by mid-season in coils on spikes above the water. The flower stalk may bend parallel
to the surface of the water. Eurasian watermilfoil reproduces by seed from buds, stem fragments, rhizomes
and root crown as the stem dies back each season.
Eurasian watermilfoil inhabits lakes, reservoirs, ponds, streams and ditches where standing or slow moving water occurs.
It is very competitive with native species and can completely dominate a plant
community within a few years of introduction. Because of the plant's ability to
form dense growths, water use activities become severely impaired.
Management steps include boat, vehicle and equipment cleaning and inspections to prevent its introduction.
Water flow and wave action prevents its establishment. Mechanical removal and mowing of the stem spreads this weed
but physical removal of the root system is effective. Herbicides are available.
Eurasian Watermilfoil infestation. Photo Credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
100th Meridian Initiative
California Department of Fish and Game
Protect Your Waters
Tahoe Resource Conservation District - Aquatic Invasives
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