Plants are the basic materials and theme of garden greening. In urban garden green spaces, trees are an inseparable part of the three-dimensional city. They can define the space between buildings and endow it with certain meanings, while also beautifying the buildings themselves. By using different tree shapes, various methods such as solitary planting, small-scale cluster planting, or large-scale belt planting can be adopted to define various spaces, provide natural landscape spots, and eliminate the adverse effects brought by the hard lines of buildings. One can imagine that if only attention is paid to the scenic spot function and architectural function of garden architecture in gardens while ignoring the role of garden plants in beautifying the environment, purifying the air, and cultivating one's sentiments, then the entire garden would become monotonous, rigid, and lack vitality. A highly ornamental landscape must achieve mutual reflection among all elements to shine.