Soil Restoration Under the Oak

 The soil under the oak tree needs some help. The soil has compacted over time, and some of its roots are exposed above ground. The root zone is not a foot traffic area, but over time, gravity and natural drainage have eroded and compressed the soil. We stopped irrigating the area years ago. The lawn died, and was replaced with moss (beautiful during the rainy winter season, but less so during the dry summer months). It's good that we stopped watering, since too much water during the warm season invites disease for oaks.

Majestic oak tree trunk and limb

I scheduled a consultation with our arborist from Brende and Lamb to discuss the health of our oak tree, and get the scoop about soil restoration. Our landscaper had expressed concerns about several small cavities and cracks in the bark at the base of the tree. We've been letting the oak leaves collect under the tree in a natural duff to jump start the soil restoration process. I wondered whether we could do more, such as bring in a load of wood chip mulch (see Wood Chips Everywhere!), or aerate the soil using a soil aerator or an air spade (a.k.a, an air knife). I also wanted to discuss irrigation, since we have plans to modernize our old, broken system.

Small cavities in the oak bark go back several inches

Our arborist has been monitoring and pruning our oak for years. He opined that the cracks in the bark were part of the natural growth pattern, and that the small cavities were probably fine since they did not harbor standing water. Limb attachments in a v-shape are more worrying, since they can trap moisture that can lead to rot (versus u-shaped attachments, where water rolls off more easily). He recommended that we bring in wood chip mulch to protect the soil, and encourage its restoration. He also recommended that under our big trees, a soaker hose  is a good irrigation solution (even oaks appreciate an occasional (monthly) drink of water during the hottest months).

Ridges and roots under the oak tree

Optionally we could aerate the soil. He thought the air spade would be overkill, since our oak is not in a high traffic area. But he described a method of using a deep-root irrigator to create holes in the soil, and then filling them with organic mulch to enable the exchange of oxygen in the soil. Many tree services offer the service, but it would be quite expensive for the area under our oak. Instead he recommended doing it ourselves - chipping away at it over time, especially during the rainy season when the soil is typically moist. It's a pleasure to meet with someone who knows and loves trees. We now have the information we need for the next steps!

Wood chips in the foreground, and leaf duff beyond