Chesapeake Bay Introduced Species Database

Myriophyllum spicatum

Common name(s):
Eurasian Watermilfoil
Eurasian Watermilfoil is native to Eurasia, and was probably imported as an ornamental plant by government workers in the 1940s and through the ornamental plant trade around the same time. The first confirmed record is from Belch Springs Pond, in Washington DC in 1942, however, there were reports from Maryland in the 1930s, but due to possible confusion with the native American Watermilfoil (Myriophyllum sibericum), the identity of those plants was never verified. After its introduction to the Chesapeake Bay region in the 1940s, Eurasian Watermilfoil spread rapidly; attaining extremely high abundances and biomasses through the 1950s and early 1960s. During this time its economic impact was the greatest as it spread swiftly across the US through the ornamental plant trade, and through aquarium and fishpond escapes, trailered boats and possibly by birds. By 1987, it was present in 34 states and 3 provinces. Today Eurasian Watermilfoil is considered an invasive weed throughout its introduced range.
Image courtesy of Paul Fofonoff.


Myriophyllum spicatum


Myriophyllum exalbescens var. spicatum

Potentially Misidentified As:

Myriophyllum sibricum; Myriophyllum verticllatum; M. aquaticum

Common Names:

Eurasian watermilfoil


Myriophyllum spicatum (Eurasian Watermilfoil) is a submersed plant (submersed aquatic vegetation).

Synonymy - Some MD authors, eg. Brown and Brown (1984); Krauss et al. (1971) have included this species in M. exalbescens Fernald (now known as M. sibiricum Komarov).

Potentially Misidentifed Species - Northern Watermilfoil (M. sibricum) is native to both North America and Asia), and very similar to M. spicatum in morphology. Reexamination of the two species by Aiken et al. (1979) shows that they are distinct. M. sibiricum's range extends south to Chesapeake Bay. Herbarium specimens collected in Chesapeake waters between the 1880's and 1942 and identified as M. spicatum were actually M. sibricum (Couch and Nelson 1985). Because of the difficulty of separating the two species, the pre-M. spicatum range and the present occurrence of M. sibiricum, in Chesapeake Bay is unknown. M. verticillatum, somewhat more distinct, has been reported from Baltimore and ponds on the Eastern Shore (Sollers 1888; Tatnall 1946). Myriophyllum aquaticum (=M. brasilense, Parrot's Feather), also introduced in the Chesapeake Bay region, has emergent stems and leaves (Couch and Nelson 1991).

This data was last modified on Wednesday, July 17th, 2013.
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