twoleaf watermilfoil USDA PLANTS Symbol: MYHE2
U.S. Nativity: Native
Habit: Aquatic Plants
Myriophyllum heterophyllum Michx.

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Taxonomic Rank: Magnoliopsida: Haloragales: Haloragaceae
Synonym(s): twoleaf watermilfoil, broadleaf water-milfoil, variable watermilfoil

Appearance
Myriophyllum heterophyllum is a perennial, aquatic herb that has leaves of two noticeably different forms.
Foliage
The submerged leaves are finely dissected, whorled, reddish/greenish-brown, and 0.5-2.5 in. (1.3-6.4 cm) long. The emergent leaves are small, oval, bright green, whorled and up to 0.25 in. (0.6 cm) wide. Emergent leaves stand 6-8 in. (15.2-20.3 cm) out of the water and may not be apparent until late summer.
Flowers
Flowering occurs from June to September. Flowers are emergent on 2-12 in. (5.1-30.5 cm), green to reddish stalks. Petals are less than 0.1 in. (3 mm) in length and are subtended by downward curved bracts.
Fruit
Fruits are small, nearly round and have a rough surface.
Ecological Threat
Myriophyllum heterophyllum is native to the southern United States, but is considered invasive in much of the northeast. This species is listed as endangered or threatened in three states (Kentucky, Ohio, and Pennsylvania).

Identification, Biology, Control and Management Resources

Selected Images from Invasive.orgView All Images at Invasive.org


Infestation;
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Foliage;
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Plant(s); Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 2: 616.
USDA PLANTS Database, USDA NRCS PLANTS Database, Bugwood.org
Additional Resolutions & Image Usage

Plant(s); USDA NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service.
USDA PLANTS Database, USDA NRCS PLANTS Database, Bugwood.org
Additional Resolutions & Image Usage

EDDMapS Distribution:
This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org
 


State(s) Where Reported invasive.
Based on state level agency and organization lists of invasive plants from WeedUS database.


Invasive Listing Sources: