The Annual bluegrass (Poa annua) belongs to Poaceae (the Grass family). It is an annual herb that is widely distributed all over the world, including various parts of Japan. This herb is commonly found everywhere, but is considered to be a naturalized plant with wheat in the old days. The leaves are linear and soft, about 10 to 30 cm high. From March to November, it grow conical inflorescences and bear a lot of light green spikelets.