The dimensions of the entire population of 19,154 street trees in urban Hong Kong had been measured in the field in a recent census. The same study also collected detailed data on the dimensions of the roadside growth space of individual trees. The results yield useful information on tree-size distribution, and its relationship with species composition, changing species preference over the years, and projected long-term arboreal character of the city. The immediate roadside environment of the trees was analyzed in terms of dimensions and types of growth space to highlight their association with tree size. The interpretations provide hints for tree managers to modify species choice with reference to attainable size and in comparison with the geometry of the planting sites. The need to take into account the ground truth in the planning and management of roadside trees in a cramped environment is emphasized. Copyright © 1997 Taylor & Francis Group, LLC.