Paspalum distichum var. distichum (knotgrass, "Kishusuzumenohie")

Japanese name: キシュウスズメノヒエ （紀州雀の稗）
Scientific name: Paspalum distichum var. distichum

[Overview]
A perennial 20–40 cm tall that prefers wet ground, found in marshes, waterways and rice paddies, where it forms colonies.
The lower part of the culm (stem) creeps along the ground, extending as much as 1 m, and spreads by rooting at the nodes.
The leaves are alternate and linear, 5–10 cm long and 0.4–0.8 cm wide, soft, and hairless on both sides.
The leaf sheaths are hairless except at the mouth.
The flower spike bears two racemes 4–9 cm long arranged in a V shape, with the spikelets in 2 rows on one side of the raceme axis.
The spikelets are oblong, 3 mm long, with very short soft hairs.
The first glume is absent, or if present, is very small and triangular and scale-like.
The stigmas are blackish purple and conspicuous at flowering.

[History]
It was collected in 1924 in Nozaki Village, Wakayama (present-day Wakayama City) by Ogawa Yoshikazu, and was identified and given its Japanese name by Honda Masatsugu.
It has naturalized in warm regions from the Kanto region southward, and has become a problem as a rice paddy weed.

[Notes]
The Japanese name comes from the plant having first been found in Wakayama.
The alternative name comes from the flower spike, which divides into two forks.

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