Both vertical mulching and radial trenching have been criticized by some researchers because these processes only affect a small area of soil and roots that are adjacent to the trench or the vertical holes. Some critics of vertical mulching and radial trenching generally prefer the stirring of the compost into the upper few inches of soil. Hendel's Tree Care & Landscaping tries to combine all three techniques. The extent of our work, however, depends upon the health of the tree. Too much root work can stress the tree.
Vertical Mulching is the process of making vertical holes in the soil usually where fill soil has been added over roots or where compaction with heavy equipment has occurred over the roots. The once restricted root is then able to grow into these holes to freely exchange needed gases with the atmosphere (for trees, this is as essential as breathing is to to us). Vertical mulching will also lessen damage due to excessive water, preserve necessary aeration during wet periods, allow sub-soil water penetration during dry periods, and promote the formation of fine feeder roots.
Some of the reasons you may need vertical mulching are:
- If your tree has been damaged during construction by heavy equipment.
- If the soil around your tree has become compacted together and is "suffocating" the tree by robbing it of the precious air it needs.
- If the drainage around your tree is poor.
- If for any reason your trees roots have been restricted in "breathing" properly.
Radial trenching is a treatment performed to trees growing in compacted or poor soils. It is a way to get oxygen to roots, replace soil, and to alleviate compaction.
Radial trenching is performed using an air-spade® to remove soil radially from the trunk out to the roots. Narrow trenches are created using high air pressure in a radial pattern throughout the root zone. These trenches appear similar to the spokes of a wagon wheel. Trenches will be 8-12 inches deep 3-4 inches wide. Using high pressure air tools causes minimal root damage.
Narrow trenches are dug in a spoke pattern around the tree, then backfilled with topsoil or compost. Root growth in the trenches will exceed root growth in the surrounding soil. A 2- to 4-inch layer of wood chips may also be added over the top of the backfilled trenches. The narrow trenches can be backfilled with the topsoil or compost. Root growth will be greater in the trenched area than in the surrounding soil. This can give the tree the added boost it needs to adapt to the compacted soil or new grade.