Barrier material installed around
the perimeter of planting bed.
Barriers are materials that trap, defect, or use chemicals to prevent tree roots from growing through the material. Since most invasive roots are growing in the first 18 inches of soil a wall of barrier material extending one inch above the soil level to twice the depth that the deepest root is found would prevent tree roots from entering planting bed. Barrier material must be one inch above ground because invasive roots can travel along the soil surface.
If trees are all around the bed then the perimeter of the planting bed will have a trench dug to the desired depth and barrier material will be installed around the bed. If only one side has trees then only that side may need to have barrier material installed. When you dig a bed you will see where roots are coming from. You may also be surprised at the distance tree roots can travel.
When installing a barrier it is important to not damage the tree. You need to know if you are destroying important roots and rooting space.
 | When this barrier material was installed both Structural roots and Critical Transport roots were destroyed. This tree could now become unstable in high winds. The tree will likely develop dead branches in the upper crown. |
 | This barrier was placed far enough away from the tree that minimal impact should be done to this tree. Some tree roots will still be impacted. But impact will be outside of the critical root zone area. |
