Low spots are localized depressions in a lawn that disrupt the smooth surface of the turf, often becoming noticeable when water pools after rain. Addressing these uneven areas is important for aesthetic uniformity and safety, as they can present tripping hazards and interfere with lawnmower operation. Furthermore, these depressions lead to poor drainage, which can suffocate grass roots in standing water and create an environment where fungal diseases thrive.
Understanding Why Low Spots Form
Low spots form due to factors affecting the underlying soil structure. A frequent cause is soil settling after excavation for utility work or irrigation lines. Disturbed soil is often loosely backfilled and gradually compacts and sinks over time, creating a surface depression.
The decomposition of organic material buried beneath the turf also contributes to settling. For example, if large tree roots or stumps were removed, the voids left as the wood fibers break down cause the ground above to collapse. Poor surface drainage can exacerbate the issue, as heavy rainfall or chronic water runoff leads to soil erosion, washing away fine soil particles. Tunneling activity by burrowing pests, such as moles or voles, can also disturb the sub-surface, causing the top layer of turf to drop into created voids.
Selecting the Right Filling Material
The material used to fill a low spot is a determining factor in the long-term health of the lawn. Simply adding heavy topsoil or clay is not recommended because these materials can suffocate existing grass blades and impede water percolation. The correct material must be porous enough to allow air and water to reach the grassroots while providing a stable base for leveling.
The most effective approach involves using a balanced blend of sand, screened topsoil, and compost. A recommended mixture is approximately 60% coarse sand, 20% screened topsoil, and 20% compost. The high sand content ensures excellent drainage and structural stability, preventing compaction. Topsoil provides essential mineral structure, while the compost introduces organic matter to support healthy root growth as the grass grows through the new layer.
Step-by-Step Guide for Repairing Low Spots
The repair process depends on the depth of the depression. For shallow low spots, defined as less than one inch deep, the topdressing method is appropriate. Begin by mowing the grass in the area slightly shorter than usual to maximize grass blade exposure.
The prepared topdressing mix should be spread thinly over the depression using a shovel. Use a landscape rake or push broom to work the material down into the turf canopy, ensuring no grass blades are completely buried. The goal is to fill the void while allowing existing grass tips to poke through the new material, promoting continued growth.
Repairing Deeper Depressions
For deeper depressions, typically exceeding one to two inches, a more intensive technique is necessary to ensure proper leveling and prevent grass suffocation. First, use a flat-bladed shovel or sod cutter to carefully slice the existing sod around the perimeter of the low spot. Cut the sod piece slightly larger than the depression, then gently roll or peel it back and set it aside to expose the underlying soil.
Fill the exposed depression with the prepared soil mix in successive layers, with each layer not exceeding two inches in thickness. This layering ensures uniform compaction and minimizes future settling. After each layer, lightly compact the material using the back of a rake or a roller. Once the filled area is slightly higher than the surrounding grade (to account for minor settling), the original sod piece can be carefully placed back. Alternatively, the area can be seeded with an appropriate grass type.
Post-Repair Watering and Maintenance
Proper watering immediately following the repair encourages the grass to root into the new material. The repaired area must be kept consistently moist but never saturated, which helps soil particles settle and encourages turf roots to grow into the topdressing mix. This requires light, frequent watering, perhaps twice daily, especially in warm conditions, for the initial week or two.
Once the grass shows active growth through the new layer, gradually reduce the watering frequency to encourage deeper root development. Regular mowing can resume once the repaired section reaches the same height as the surrounding lawn. Some slight settling may still occur over the following weeks, and a second, small application of the topdressing mix may be necessary to achieve a level surface.