The street trees are one of urban ecosystem where are exposed to harsh environmental stresses for plants. It is revealed that flora under the street trees is homogeneous in Europe and USA even though climate zones are different from each other. However, there is no intensive study about flora under the street tress in East Asia. To understand characteristics of ecosystem under street tree in East Asia, three major approaches to investigate flora and its phenology under the street trees were developed. 1) Through intensive flora investigations equipped with android app of the Biodiversity Observation Database (BODB; http://www.biodiversitydb.org/intro.php), East Asia also shows homogeneous pattern of flora but different species composition from Europe and USA. 2) Correlation between weed diversity and micro-environmental features was calculated based on both geographical coordination of flora researches and microclimate minute-data provided by Korea meteorology Administration. 3) Dynamics of flora and phenology under the street trees were monitored periodically. In total, four countries, 162 sites, 3,148 street trees, 18,828 pictures were collected and 27 street tree species and 117 species have been identified under the Street Tree Flora Database (http://streettree.infoboss.co.kr/intro.php). Through diverse analyses, biodiversity of flora under the street trees in East Asia was unraveled, biological niche under the trees affected by micro-environments, and dynamics of flora under the trees was deeply analyzed. These results and platform for managing data will provides intense insights of understanding micro-ecosystems under the tree in near future.