Root and Soil Care

Foot traffic, vehicles, and construction can compact soil and reduce the pore space between soil particles. This limits the gas exchange and water retention that roots depend on. Compacted soil is not able to hold as much water for the tree to access during dry periods and roots have less access to oxygen and nutrients, which in turn reduces growth and can contribute to long term decline.

Urban development often strips topsoil from the site, leaving trees growing in subsoil that lacks the organic matter, microbial activity, and nutrient availability that enables trees to thrive. The remaining soil frequently has high pH and poor structure, further limiting what roots can access.

Raising or lowering the soil grade around an established tree can have serious consequences for root health. Adding fill soil over the root zone reduces oxygen availability and can suffocate roots that were established at the original grade. Cutting the grade removes roots outright and can destabilize trees that depended on them for structural support. Either scenario disrupts the root environment that the tree developed around, and the effects may not become visible for several years after the grade change occurred.

Trees grown in nursery containers can develop roots that circle the inside of the pot before they are planted. If these roots are not corrected at planting, they continue to grow in that circular pattern and can eventually constrict the flow of water and nutrients between the roots and canopy. Girdling roots are a common but frequently overlooked cause of decline, and in many cases are hidden beneath the soil surface where they can only be identified through excavation of the root collar.

Compacted soil can be decompacted using the air spade to fracture and loosen the soil profile around the root zone without disturbing the roots themselves. We typically amend the backfill with compost and other organic materials to improve soil structure, water retention, and microbial activity. The result is a root environment that is better able to support the tree's long-term health and recovery.

The root collar is the point where the trunk transitions to the root system, and it needs to be at or just above the soil surface to function correctly. Buried root collars are common in urban trees — caused by improper planting depth, soil settling, or grade changes over time — and can lead to bark decay, girdling roots, and long-term decline. Root collar excavation uses the air spade to carefully remove excess soil and debris from around the base of the trunk, exposing the root collar and creating conditions the tree can actually thrive in.

Vertical mulching is a soil aeration technique used to improve gas exchange and water infiltration in compacted root zones. A pattern of narrow holes is drilled through the compacted layer and backfilled with organic material, creating channels that allow air, water, and nutrients to penetrate deeper into the soil profile. It is a less invasive alternative to full air spade decompaction and can be an effective option for treating larger root zones or areas where access is limited.