An important step in the cultivation of super prematurity strawberry is how to determine the start of flow bud differentiation (FBD),and this is the premise of planting strawberry at the early stage.We conducted experiments Fragaria ananassa cv.‘Benihoppe’ at low-temperature treatment (nocturnal temperature was 17~20 ℃ with fluctuations) and short-photoperiod treatment (dark length was 16 h) from 23rd June through 24th August 2011.From the start of treatments we took samples every 3 to 5 days,separated apexes under anatomical microscopy,fixed all materials with FAA,dried at critical point,and observed them with scanning electron microscope.On the basis of the observed micro-morphological characteristics,we divided the whole process of strawberry flower bud differentiation into 7 phases:flower bud non-differentiation phase,FBD starting phase,reproductive apex swelling phase,inflorescence differentiation phase,top-flower sepal formation phase,flower petal formation phase,stamen formation phase and pistil formation phase.In the flower bud non-differentiation phase,the top bud was in the state of vegetative growth continually.In the FBD starting phase,the top bud turned gradually from sharp,narrow vegetative apex into smooth,broad reproductive apex.In the reproductive apex swelling phase,the reproductive apex uplifted and swelled.In the Inflorescence differentiation phase,top flower primordium and lateral flower primordium gradually appeared during top flower primordium differentiation process.In the top flower sepal and petal formation phase,the differentiation of sepal (including accessory sepal) and the petal was finished.In the stamen formation phase,two-wheeled stamen primordium appeared gradually by differentiation.In the pistil formation phase,a large number of pistil primordium uplifted gradually,the carpel primordium curled,and the FBD process was complete.This result revealed that the suitable time of strawberry planting is after the reproductive apex fully swellen.That is after the low-temperature and short-photoperiod treatment 15~20 days,the strawberry seedling can be planted on field.