Frequently Asked Questions

A general rule of thumb is to install 2 cubic feet for every square foot of tree crown expected at maturity.  The depth should be 24” minimum, but 36” is preferred. 

Structural Soil was developed by River Sand, Inc. for urban tree landscapes.  The design specifies the type of gravel, soil, and additives by type and quality for a tested, proven structural soil mix. 

Structural soil is a type of Urban Tree Planting Mix.  Structural Soil is used for planting trees in urban settings, typically surrounded by concrete sidewalks or roads, to allow for both compaction to support infrastructure but at the same time providing soil structure for root growth.  Structural Soil allows trees to survive and thrive in urban settings usually along the sidewalk, and helps prevent tree roots from cracking or damaging concrete or asphalt. 

The sand-based structural soil blend design uses sand, usually coarse in texture, as the primary medium.  The gravel-based structural soil blend uses gravel, usually larger sized and washed, as the primary medium.  Both still include a portion of clay or clay loam soil along with soil amendments such as hydrogel. 

Most structural soil is used along sidewalks and roadsides for planting trees.  The structural soil is placed in a specified area for each tree to encourage root growth within the cell, and not outside the cell which will lead to concrete/asphalt cracking or damage.  Healthy trees are able to grow and add long-term benefit to an urban landscape without creating safety issues from cracked pavement for pedestrians and vehicles.