Myriophyllum verticillatum

Whorled Water Milfoil

Comb Water Milfoil

NATIVE TO MAINE

NOTE: All leafy milfoils display a wide range of vegetative variability. All milfoils found in Maine waters should be considered “suspect” as potential invaders until a positive identification has been confirmed.

Habitat: Whorled water-milfoil is found in the submersed plant community. It can grow in shallow water in coves of lakes or slow-moving streams.

Description: Whorled water-milfoil is a submersed aquatic plant with feather-like finely divided leaves, each leaf comprised of 9 to 17 pairs of thread-like leaflets. The leaves are arranged in whorls (4 to 5 leaves per whorl), spaced about 1 cm apart along the stem. Flowers occur in the axils of bracts, arranged in whorls around a slender spike that emerges upright 4 to 10 cm from the surface of the water. The bracts are longer than the flowers or seeds, up to 1.5 cm long, and pinnate or “comb-like” a feature referenced in this plant’s alternative common name. 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.

Range: Whorled water-milfoil is a native plant, scattered in New England, New York, Indiana, Illinois, Nebraska, Utah, and Canada. It is relatively uncommon in Maine.

Annual Cycle: Turions provide the primary means of winter survival for northern water-milfoil. Produced toward the end of the growing season, the turions eventually separate from the parent plant, and remain dormant until the following spring when they unfurl and take root. The emergent flower spikes form early to mid summer, but reproduction by seeds is not common. Like most other milfoils, whorled water-milfoil propagates readily by fragmentation. Some water milfoils are known to hybridize with each other.

Value in the Aquatic Community: Whorled water-milfoil is a food source for wildlife including water fowl. The plants provide shade and cover for fish and insect larva.

Look Alikes: Whorled Water Milfoil may be confused with other Water-milfoil species, water marigold, coontail, common bladderwort, white water crowfoot, yellow water crowfoot, fanwort, prickly hornwort, or mermaid-weed.