Building a tree ring
In addition to being an attractive design element, a border encircling a tree is practical in many ways. It protects the tree trunk from contact with lawn mowers, and it corrals mulch from spreading to the lawn. Plus it adds a decorative element to a garden. Depending on the height of the border and the material used, a tree ring can provide a pleasant seating area, as well.
When building a tree ring, be sure to cut the trench for the base layer of blocks as shallow and as far away from the tree roots as possible. To allow air to circulate to around the bark of the tree it is important to protect the base of the trunk from a buildup of soil or mulch. Also, it’s good to preserve the established soil depth that covers the tree root system.
Buy the blocks or bricks before you mark out the layout. In this way you can plan the diameter of the ring to fit the size of the blocks or bricks and avoid having to cut them to fit. If the tree is young, be sure to make the ring large enough to plan for growth. Remember that the farther out you go from the trunk, the easier it will be to trench. Lay the blocks or bricks around the tree as a guideline and then use sand to mark the position.
1. Dig a trench about 30cm deep and a few cm wider than the base course of block. Compact the soil with a tamper.
2. Add gravel in 5cm. layers, tamping after each addition.
3. Lay the base course of block. At least half of the first block should be below the finished grade to prevent shifting.
4. Backfill and front-fill the trench with gravel and tamp to compress the gravel.
For subsequent courses of block, use blocks that are faced on the front and back so it’s attractive from the inside, as well. Apply a bead of construction adhesive between the layers.
5. You can add a thin layer of topsoil for planting flowers inside the ring, but no more than a top dressing - so the tree roots can breathe. Keep in mind that additional vegetation will compete with the tree for moisture and nutrients, so feed and water accordingly. Mulch is best; a 3 to 5cm layer helps to retain moisture and block weed growth. Remember to not cover the base of the trunk.