twoleaf watermilfoil, twoleaf watermilfoil, broadleaf water-milfoil, variable watermilfoil
- Myriophyllum heterophyllum is a perennial, aquatic herb that has leaves of two noticeably different forms.
- 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.
- 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.
- 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).
- Global Invasive Species Database. 2011. Invasive Species Specialist Group (ISSG) of the IUCN Species Survival Commission
- University of Florida, IFAS Extension, Center for Aquatic and Invasive Plants
- Invasive Plant Atlas of New England (IPANE)
- Flora of China, www.eFloras.org
- USDA NRCS PLANTS
- USDA ARS GRIN
Images from Bugwood.org