Hello! I’m hoping you can help me. I have two lindens at the side of my house in downtown Toronto under which is moderately compacted soil and debris from my recent renovation. And under one of the trees the soil is burying the root flare of the tree. I would like to plant a ground over under the trees (something that will tolerate dry shade). My question is: what are the steps I should take before planting the ground cover? How best to deal with the compaction without damaging the tree roots? How best to dig away the mound of soil to free the root flare? (the mound is full if roots). Is it ok to add compost around the trees or will this further bury their roots? Any tips/advice would be greatly appreciated. Thank you!
Thank you for your inquiry. In dealing with soil compaction you have a few issues to deal with as a result of. Poor nutrient uptake by plants/trees, soil prone to drought and low levels of oxygen are all negative consequences of this issue.
The most viable solution for a homeowner is to apply 5-8 cm (2-3 inches) deep of compost, mulch or wood chips over the compacted area. This will cause nutrients and beneficial microbes to work their way into the compacted soil, and as a result, loosen and aerate the soil. This is much safer than any method that could disturb the tree roots and is a proven method long term. Out of the three different amendments above, compost will work the fastest in restoring things to a healthy soil condition. Wood chips or mulch would be slower but produce similar results. Don’t use store bought “ornamental” mulch in this sort of application as it won’t provide a significant nutritional benefit to the compacted soil.
Compost is probably the best choice for you considering you wish to plant ground cover in the area in the near future.
Adding these natural soil amendments will not further compact your roots at all. Our natural forest trees are grown in abundant soil just like this with the layers increasing each year from naturally composting dead organic materials. Best of luck in restoring your compacted soil.