Najas graminea

Najas graminea, also known as ricefield water-nymph is a species of aquatic plant found in freshwater habitats, especially still or slow-moving waters, like ponds and rice fields. It grows to a maximum length of 30 cm. The flowers are monoecious. The flowering season is from July to September. The natural distribution of this annual plant covers most of Africa as well as the Middle East, Central Asia, East Asia, Southeast Asia, New Guinea, New Caledonia and northern Australia. It has become naturalized in Spain, Italy, Bulgaria, Crimea and California. This plant is also commercialized in the aquarium trade....read more on Wikipedia.