Trees require adequate supply of uncompacted, well aerated, and moist soil in order to thrive. These soil conditions enable tree roots to obtain all the essential elements they require for healthy growth – nutrients, oxygen, and water. They also happen to be the elements found in the soil of natural forest settings. In built-up urban areas however, these soil circumstances are often unavailable. In this eBook, we provide a soil quality definition and explain the soil requirements of urban trees.

Soil is the uppermost layer of the earth’s crust and is the medium in which trees and other plants grow and spread their roots. Soil is comprised of finely ground rock particles and materials such as sand, silt, clay, and gravel; with void spaces between particles containing air and water.

Although some potential urban soil limitations can be addressed with species selection – such as spatial constraints, soil PH, wet & dry soil, and even salt contamination – one soil condition that cannot be mitigated by plant selection is compacted soil. Adequate provision of quality, uncompacted soil is essential for the long term success of urban trees.

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