American sloughgrass belongs to Poaceae (Grass family). It is an annual herb that is distributed all over Japan, Korean Peninsula, eastern Siberia, Central Asia to eastern Europe and North America. It was introduced into Japan with wheat in Yayoi Era (about 2500 years ago). This herb occurs in rice field linches and can reach 30-90 cm in height. The leaves are linear and tinged with whitish green. The clusters are borne from June to July, and dense pale green spikelets on one side of branchlets.