PURPOSE: To raise seedlings of strawberry within a short period and to obtain a large quantity of grown strawberry seedlings, by collecting a nondisease mother seedling from tissue-cultured seedlings and proliferating the mother seedling in a vinyl house under a definite condition.

CONSTITUTION: Raw seedlings grown by tissue culture are managed at 15W25°C under a light of a fluorescent lamp of 2,000 Lux or thereabout preferably in September or thereabout for 15hr per day. Dormancy of strawberry is avoided during the above period to obtain a nondisease mother strain in the middle of December or thereabout. The mother stock is planted in a vinyl house, the temperature in the house is maintained at ≥10°C and the generation of runner is promoted by removing flower buds. For example, ≥1,500 planting seedlings can be prepared from single mother stock in half a year. The troubles of abnormality and modification of the seedling can be absolutely eliminated because the proliferation is carried out by natural proliferation with a runner.