Lysimachia mauritiana Lam. (Primulaceae), a biennial maritime plant, is widely distributed in East Asia, the Philippines, Micronesia, Polynesia, and the Indian Ocean. Because of this species’ wide distribution in Japan, we hypothesized that it could germinate and grow even in the bare coastal areas damaged by the tsunami caused by the Great East Japan Earthquake. Thus, we aimed to evaluate the seed germination of L. mauritiana under different sowing depths, temperatures, and salinity soil conditions. The highest germination rate was obtained by sowing L. mauritiana seeds near the soil surface, with germination rate decreasing as the seeding depth increased. Lysimachia mauritiana germinated even at relatively low temperatures. Moreover, we found that L. mauritiana seeds could germinate in less than 1% salt water and in salt-accumulated soil, using soil soaked in 5% or 10% salt water. Our results therefore suggest that L. mauritiana seeds could germinate by sowing on the bare soil surfaces damaged by the tsunami.