Trees are important to the composition of urban design proposals. Drawings and sections show healthy, mature trees lining streets and punctuating plazas. There is an unspoken conclusion that a street without trees is not a complete street. Yet there is a critical component missing from most of these renderings.
Drawings almost always show the tree magically rising out of the ground plane with no means of support. Typically the sidewalk paving is shown right up to the trunk of the tree, the critical swelling of the trunk flare at the base of each tree above ground is not drawn. Also unspoken is the assumption that the trees will somehow find rooting space. The messy details of how the tree grows are left to the next phase of the design process. To be fair, urban design drawings, particularly the ubiquitous “typical” sections, also omit the building and light pole foundations. These omissions in the beginning of the planning process are to be added as the project moved forward. It is reasonable to assume the engineers and architects will put foundations under buildings and light poles, unseen structures typically built into the very first cost estimates. But sadly and all too often, the tree’s requirements and cost are ignored throughout the entire process.
There are two basic elements of the tree that urban designers must incorporate into their drawings, reports, and cost estimates. These are (1) sufficient soil volume to support the size tree expected to grow and (2) acknowledging the structural requirements of the tree where it meets the ground.