M. heterophyllum is an aquatic plant that has submerged vegetation with emergent flowering spikes. Plants hermaphroditic, occasionally monoecious. Stem stout, to 100 cm;internodes crowded. Submerged leaves 4- or 5-whorled or scattered, pectinate, oblong in outline, (1.5-)2-4 × 1-3 cm;segments in 5-12 pairs, filiform, 0.5-1.5 cm. Inflorescence a terminal spike of 4-whorled flowers, 5-35 cm, in monoecious plants lowermost flowers female, uppermost ones male;bracts persistent, eventually reflexed, lanceolate to oblong or obovate, 4-18 × 1-3 mm, margin sharply serrulate;bracteoles ovate, ca. 1.2 × 0.6 mm, margin serrate. Petals 1.5-3 mm. Stamens 4. Fruit 4-loculed, subglobose, 1-1.5 mm;mericarps with 2 finely tuberculate ridges abaxially, apex beaked (Flora of China Editorial Committee, 2012).
Morphological keys (such as Aiken, 1981) are available but rely mostly on characters of flowers and fruits, which may not be present, as M. heterophyllum rarely flowers. It can best be recognised by its dense underwater growth and undivided, serrate emergent leaves (Q-bank, 2015).
Genetic identifications using the nuclear ribosomal DNA internal transcribed spacer regions (ITS) have become common (Moody and Les, 2002;Thum et al., 2006).
Related invasive species
- Myriophyllum heterophyllum
Related Farm Practice
- Flora
M. heterophyllum is an aquatic plant native to southeast USA. It is considered invasive throughout New England and northwest USA and as an emerging invader in Europe because of its tendency for uncontrolled growth and subsequent formation of dense mats of submergent vegetative material throughout the water column and at the water surface. These mats prevent water flow, reduce sunlight, reduce oxygen availability, and impede swimming, boating and fishing. M. heterophyllum is banned from sale in some New England states and Washington state.