Silica accumulation in long-lived leaves of Sasa veitchii was investigated using the molybdenum blue method. In general, silica accumulation was rapid during spring and summer, and slow during winter. The leaves continuously accumulate silica throughout their life. The significance of these observations is discussed in relation to two hypotheses for silica accumulation in plants: (1) that silica accumulation is a result of water consumption by the plant: and (2) that silica is actively accumulated to protect the plant. The results of the present study support the former hypothesis.