Myriophyllum spicatum

Plants

Eurasian water-milfoil, Eurasian watermilfoil, myriophylle en epi, spike watermilfoil, spiked water milfoil

The native and introduced ranges of Myriophyllum spicatum (Eurasian Watermilfoil) are somewhat obscured by confusion with M. sibericum (= M. exalbescens, Northern, Siberian or American Watermilfoil), which appears to be native to both Eurasia and North America. Nonetheless, this submerged aquatic plant M. spicatum is clearly an Old World species introduced to North America.  It was probably imported as an ornamental plant by government workers. The first verified record of M. spicatum was a collection from Belch Springs Pond, in Washington DC in 1942. This plant spread rapidly in the northeast United States in 1940's and 1950's. Separate introductions through the ornamental plant trade probably occurred occurred in Western states at this time (Couch and Nelson 1985; Couch and Nelson 1991). In all the invaded regions, M. spicatum was spread by aquarium and fishpond escapes, trailered boats, and possibly by birds. It is now present in 46 states.  It was first reported form the San Francisco Bay Delta in 1979, and from the Columbia River estuary by 1981.  This plant grows well in salinities up to 13 PSU, and can tolerate higher salinities for brief periods.  It has been considered highly invasive in early stages of its spread in Chesapeake Bay and many lakes, but has become regarded as a beneficial species of submerged aquatic vegetation in many locations, possibly stabilized by herbivores and diseases.