PURPOSE: To shorten the growth period to development of fruit bodies by cultivating SHIITAKE or KURITAKE mushrooms on steam-sterilized wood of appropriate length.

CONSTITUTION: Trees for cultivating mushrooms are cut into appropriate lengths and sterilized with hot water or steam. Thus, other various germs are killed and the trees also are killed simultaneously, even if they are alive. This treatment causes no abnormality in the tree tissues such as cracks, compared with decayed trees. When the seed of mushrooms is inoculated to the treated trees, the growth of mycelia is mush improved and fruit bodies can be formed in a shortened period.