Briza maxima L. are exotic plants in Japan, which come from Europe. We studied seed germination to find the causes of their naturalization. The seeds germinated very little for three months after the seed collection, and showed characteristics of photoblastic seed. But many seeds could germinate under both light and dark conditions from four months after the seed collection; especially, they showed above 50% of germination nine months after seed collection. The seeds have characteristics of dormancy since when the seed germination percentage is low for three months after the seed collection, but these seeds germinated much with GA3. The seeds could germinate from 10 to 25℃ well with the exception 30℃. The seeds stored under dry condition of room temperature showed above 50 % after 16 years old. The Briza maxima seeds showed orthodox characteristics and could keep germinability for long time under dry condition. The Briza maxima plants have been distributed in pacific belt zone in Japan. The seed germinability for long time under dry condition was considered possible to increase the distribution in urbanized areas.
