New York Natural Heritage Program
Water Milfoil
Myriophyllum alterniflorum DC.
Myriophyllum alterniflorum USDA
Family: Water-Milfoil Family (Haloragaceae)

State Protection: Threatened
listed species are those with: 1) 6 to fewer than 20 extant sites, or 2) 1,000 to fewer than 3,000 individuals, or 3) restricted to not less than 4 or more than 7 U.S.G.S. 7 minute topographical maps, or 4) listed as threatened by U.S. Department of Interior.

Federal Protection: Not Listed

State Rarity Rank: S2
A State Rarity Rank of S2 means: This plant is threatened/imperiled in New York because of rarity (typically 6-20 populations or few remaining individuals) or is vulnerable to extirpation from New York due to biological factors.

Global Rarity Rank: G5
A Global Rarity Rank of G5 means: This species is demonstrably secure globally, though it may be quite rare in parts of its range, especially at the periphery.

Did you know?
The genus name Myriophyllum comes from the Greek, murios (myrios), "countless, infinite", and fullon (phyllon), "leaf; foliage"; hence "many leaved". Small fish and aquatic invertebrates use this plant for shelter. Most populations in New York are large and contain thousands of plants.

State Ranking Justification [-]
There are only 13 verified occurrences, and 11 historical records in the state. Only two of the existing populations have 100 or more plants. Most occurrences lack accurate counts or estimates of population size. Only 3 of the sites have been visited since 1993.

Short-term Trends [-]

Long-term Trends [-]