Well-planned squares are important spaces that can ensure quality of life and contribute to the urban biodiversity conservation. These places have been socially and economically important since their creation, and more recently their environmental contribution and aesthetic importance have been highlighted. Vegetation in squares is an important indicator of environmental quality. Therefore, data acquisition and monitoring are necessary for decision-making aimed at improving urban environments. The tree-shrub composition in squares should be evaluated along with spatial and coverage indices traditionally used, since these indices in isolation do not provide sufficient information for proper planning. Other information, such as estimated permeable area and proportion of local native species, also help to guide planning decisions in the management process to create better spaces, allocate resources for maintenance, and improve public use. The planned tree-shrub composition in squares occurs together with the development of other functions, aesthetic and functional, which can be considered indicators of the quality of these open spaces. This chapter proposes: (a) to present an understanding of squares from the perspectives of geography, landscape architecture, forestry, and biological sciences; (b) to highlight the process of insertion and recognition of the role of vegetation in que quality of these public spaces, mainly in Brazil; (c) to propose a set of environmental indicators for the characterization and assessment of vegetation in squares to contribute to the urban biodiversity conservation.