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Twoleaf Watermilfoil (Myriophyllum heterophyllum Michx.)

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Range - Expand

Native or Not Present
Introduced or Not Present
Native or Expanded

This tentative map is based on our own research. It may have limited data on Canada and/or Mexico, and there is some subjectivity in our assignment of plants as introduced vs. expanded. Read more in this blog post.

This species is generally agreed to be native to much of the US and eastern Mexico, but to have expanded its range into the northeast, where it is not native. We found conflicting data on where it was native; VASCAN shows it native to NB, ON, and QC but if it is expanded in New England it is probably expanded in at least NB and perhaps all three provinces. It also has been introduced in the Pacific Northwest. Go Botany lists it as introduced in Texas, but we found no justification for this claim and suspect it is a data error perhaps due to the genus being marked as a Noxious weed in Texas; FSUS shows it as Native to Texas and Aiken (1981) has reported it as such and we found no explanation to the contrary. Our map is complete for Canada but we have yet to build the portion of its map in Mexico.