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Urban/suburban design to support trees

tree in islandTrees grow poorly in urban areas unless the soil beneath and adjacent to hard surfaces supports root growth. Root growth is THE critical factor for successful design execution! The system has to be specially designed to accommodate tree root growth. This does not happen without careful planning, and execution. Occasionally, portions of cities get lucky and trees grow despite poor planning. These examples should not be used as models for future design because these are usually anomalies.

Minimum soil volume for trees
ultimate trunk diameter soil volume
16 inches 1000 cu. ft.
24 inches 1700 cu. ft.

Minimum soil volume required to support reasonably healthy trees can be summarized in the table to the left. This soil should be at least three feet deep and must have a bulk density below the critical value for the soil type. Rooting space needs to be wider if it can not be three feet deep. Place trees as far from hardscape as possible.

Tip: Plant the easy places first because it costs less.
Good examples
| Site modifications | Root conflicts | Sidewalks | Parking lots | Street trees | Special planting situations | Tree spacing | Tree selection | Tree preservation

Fact sheet: Urban design to support trees (pdf)