This study attempts to contribute planting design theory by providing a visual analysis of, and in the aesthetic sense an alternative scenario for, planting design practices in urban parks and greenspaces. In the study, plants are regarded as effective elements and an expression of form and texture. A matrix is developed to assess their formal effects by experts. Development of the matrix incorporates visual properties of plants, basic design principles, and Gestalt theory. Visual analysis of existing planting design practices in six different silhouettes in two urban parks and an alternative planting design scenario is then suggested. This study, developing a method to analyse a landscape silhouette, provides clues to produce ideal silhouettes in terms of formal aesthetics using design principles. It is suggested that there is a potential for landscape researchers to further develop this method using other variables of formal aesthetics and Gestalt principles and in other settings.