It is common sense that a newly planted tree has to establish its root system to call the new location its new home for many years in the future. When a new tree is planted in the built environment, the soil compaction is guaranteed due to the compaction by the site preparation or the working vehicles that do the landscaping. The soil can be so compacted that root growth is prohibitive. So digging a planting hole that is two to three times the rootball size is recommended by professionals. However, it would cost the contractor more. Because the lowest bidder typically wins the job, they do not budget the extra care required for trees to be properly established.

From the beginning, we have recommended people use TreeDiaper^® sizes double the rootball sizes or at least 20" larger than the rootball. I wrote two blogs in the past about this:

https://www.treediaper.com/blog/please-also-water-the-surrounding-soils-of-a-newly-planted-tree

https://www.treediaper.com/blog/why-we-go-back-to-recommendation-solely-based-on-rootball-sizes

We also developed a size calculator for people to find out the recommended size: https://www.treediaper.com/products/calculator

Nevertheless, we have cases where people would use TreeDiaper^® sizes that are the same or smaller than the rootball sizes. Below is a case where TreeDiaper^® TD36 treemats worked well for trees of 20-inch rootballs, but not so much for rootballs 40" or larger. Trees were planted in the spring of 2023, the following pictures were taken in October 2024. So these trees have been planted for 17 months or two growing seasons. Around the time these pictures were taken, the region (Hanover County VA 23005) is under moderate drought conditions (eventually there was 0.36" in 41 days).  

For the 80 trees with 20" rootball on this site that were installed with TreeDiaper^® TD36R treemats, the trees are alive and establishing. 

Out of the 8 trees with rootball sizes 40 inches or larger (3.5-5” caliper or larger), 5 survived. All 5 are smaller ones than the dead ones.

I also spotted three trees (with about 20" rootballs) without TreeDiaper^® TD36R treemats for unknown reasons. Two of these three trees have died.