Dear Friends of Maine Lakes, Thank you for visiting our Interactive Field Guide! Though the primary content pertaining to species identification in this Guide is—for the most part—still correct and useful, the site itself is no longer fully-functional (nor able to be updated). The entire Guide will soon be replaced by a new, expanded website-version of the Maine Field Guide to Aquatic Phenomena. So please stay tuned! Thank you for your patience!

Go to VLMP Home Page


Milfoil comparison table
Milfoil comparison table

Myriophyllum verticillatum


Whorled Milfoil colony
Whorled water-milfoil in-situ

Description: Whorled water-milfoil has two distinct leaf types: submersed leaves and emergent leaves (called bracts). The submersed leaves are finely a href="Glossary.php#Feathered">feather-divided, with 5 to 14 thread-like leaflet pairs per leaf. Whorls of 4 or 5 leaves are spaced (up to 1 cm apart) along the stem. Whorled milfoil produces flowers and fruits above or at the water's surface on erect (4 to 15 cm) spikes. The bracts occurring on the emergent spike are pinnately lobed (like a double-sided comb). Even when fully developed, the flowers are very small. (A hand lens may be needed to study this feature.) The bracts are typically two or more times longer than the flowers and fruits. Toward the end of the growing season, elongated club-shaped winter buds (or turions), comprised of small stiff leaves, are formed along the submersed stems.

whorled water-milfoil Range Map
U.S. range map of whorled water-milfoil

U.S. Range: Whorled water-milfoil is native to Maine, new England and to other parts of the United States.

Look Alikes: The native milfoil that whorled water-milfoil most closely resembles is northern water-milfoil. Whorled milfoil may also be confused with two fo the invasive milfoils: variable water-milfoil, and Eurasian water-milfoil. Whorled water-milfoil is the closest native look alike to variable water-milfoil.

Print out a copy for the field
(Adobe Acrobat file) - To get the free Acrobat Reader go to


Click Images for Larger Version
Whorled Water Milfoil winter buds Whorled Water Milfoil in-situ Whorled Water Milfoil range map Whorled Water Milfoil illustration Whorled Water Milfoil fruit illustration

Secchi Disk
Water Quality Monitoring
Invasive Target
Aquatic Invasive Monitoring

Maine Volunteer Lake Monitoring Program
24 Maple Hill Road, Auburn, ME 04210

2009 Maine Volunteer Lake Monitoring Program | website comments to:

bottom wave