A GIS-based method for locating potential tree-planting sites based on land cover data is introduced. Many factors need to be considered when selecting sites for trees in an urban environment. Important site conditions related to tree selection include factors, soil characteristics, environmental conditions, planting space, site location, existing vegetation, aesthetics, land ownership and regulations. Criteria are developed to identify locations that are spatially available for potential tree planting based on land cover, sufficient distance from impervious surfaces, a minimum amount of pervious surface, and no crown overlap with other trees. In an ArcGIS environment, a computer program is developed to iteratively search, test and locate potential tree-planting sites by virtually planting large, medium and small trees on plant able areas, with large trees given priority as more benefits are expected to accrue to them. A study in Los Angeles, USA found that 2.2 million potential planting sites, approximately 109.3km2 of potential tree canopy cover.