Japanese name: オオフサモ（大総藻） Scientific name:Myriophyllum aquaticum
[Overview]
A perennial found in ponds, swamps and waterways.
An emergent aquatic plant.
It has rhizomes.
The stem is cylindrical, branching as it extends far through the water, and produces roots from the nodes.
On the stems extending above the water, 3–7 leaves per node grow in whorls, each 2–5 cm long and finely pinnately divided.
The leaves are tinged with a powdery white.
The plant is dioecious, and only female plants are known in Japan.
White-green flowers about 2 mm long are borne in the axils of the leaves above the water.
The flowers have no petals.
Because only female plants exist in Japan, it does not set fruit and reproduces vegetatively.
[History]
Plants introduced around 1920 as ornamentals have become naturalized in various places.
[Notes]
It is designated a "Specified Invasive Alien Species" under the Invasive Alien Species Act.
