Using a combination of mechanical and representative sampling, plots in 13 cities of the Yangtze River Delta Region were surveyed in 2015—2016; the survey consisted of 449 plots across 76 urban parks, roads, and waterfront greenbelt areas. As part of this study, we analyzed the factors and drivers for species composition, distribution, size, coverage, and growth vigor of the predominant trees located in the urban plots; the data provides a scientific basis for the future construction of forest cities and the improvement of urban human settlements. The results show that: ① In total, 157 tree species were recorded in the surveyed plots, which belonged to 115 genera and 54 families. The dominant families belonged to the Rosaceae group (20 species across 12 genera), with a high proportion of single families and relatively dispersed species composition. ② The plots were characterized by significant temperate features (73 genera), showing that the tree species have typical temperate properties in application. ③ The main tree species of the urban man-made forests were Cinnamomum camphora and Platanus × acerifolia, with coverage reaching 27.45%; specifically, Cinnamomum camphora was the dominant species. The utilization of trees across different types of urban plots varied considerably. ④ It was found that tree species with 10 cm ≤ D≤ 30 cm constituted the majority of tall trees in the urban plots, including many species of native trees such as Sapindus saponaria, Koelreuteria bipinnata 'Integrifoliola', and Liquidambar formosana. The quantity and distribution of the trees, however, was found to be extremely unbalanced. The coverage of Cinnamomum camphora and Platanus × acerifolia in the area was as high as 45.18%, and the relative species diversity and community stability were found to be weak. We recommend that the coverage of other tree species is gradually increased in the future construction of urban plots.