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).