A bumpy lawn, characterized by low spots, humps, and divots, detracts from the aesthetic quality of a landscape and creates practical problems. Mowing an uneven surface can lead to “scalping,” where the mower blade cuts the grass too short on high spots, causing stress and discoloration. Moreover, an irregular lawn surface can act as a tripping hazard, limiting the usability of the yard for recreation.
Identifying the Sources of Unevenness
Addressing lawn unevenness requires identifying the underlying causes, as fixing the symptom without correcting the root problem means the bumps will likely return. Natural soil settling is a common factor, particularly after new construction, or when organic material like old tree roots and buried debris decomposes, leaving a void that causes the surface to collapse.
In regions with cold winters, the freeze-thaw cycle known as frost heave can create bumps as the soil expands and contracts unevenly. Tunneling pests, such as moles and voles, are another source of disruption, pushing up soil to create surface mounds and subsurface tunnels. Water movement also plays a significant role, where poor drainage or excessive runoff can cause soil erosion, washing away material from high spots and depositing it in low areas.
Preparing the Site for Leveling
The success of any leveling project depends on proper preparation, which should ideally occur during the active growing season, such as spring or early fall. This timing allows the turf to recover quickly from the work. Warm-season grasses, like Bermuda grass, respond best to spring leveling, while cool-season varieties, such as fescue, benefit from work done in late summer or early autumn.
Before applying any leveling material, the grass should be mowed to a very short height, often the lowest setting recommended for the turf type, to expose the soil surface. If the lawn has excessive thatch or heavily compacted soil, dethatching or core aeration may be necessary beforehand to improve soil structure and allow the leveling mixture to reach the root zone. Tools for the task include a garden rake, a long straight edge or leveling lute, and the appropriate topdressing mix.
Using Topdressing for Minor Surface Imperfections
Topdressing is the preferred method for correcting minor surface imperfections, specifically shallow dips and undulations less than one inch deep. The ideal topdressing mixture is a blend of fine sand, compost, and topsoil, often mixed in a ratio like 50% sand and 50% topsoil, or 70% sand to 30% loam. The high sand content allows the material to spread easily and settle into low spots without compacting the existing soil.
The mixture should be applied thinly, with a layer no greater than half an inch (about 10 millimeters) at any one time, to prevent suffocating the grass plants. This material is spread over the low spots and then worked into the turf using the back of a rake or a push broom. The goal is to fill the depression while still leaving the tips of the grass blades exposed to continue photosynthesis. If a low spot is deeper, the process must be repeated in stages, allowing the grass to grow through the previous layer before adding more material.
Repairing Deep Ruts and Significant Bumps
When dealing with deep ruts, large humps, or depressions exceeding one to two inches, a more invasive technique than simple topdressing is required. This process involves temporarily removing the existing sod layer to access the underlying soil structure directly. The perimeter of the affected area is first cut using a flat-edged spade or sod cutter, creating a clean boundary where the sod can be lifted and peeled back.
For a low spot, quality topsoil or the leveling mixture is added beneath the exposed area and tamped down to the desired height, accounting for slight settling. For a high spot, soil is removed until the base is level with the surrounding ground.
Once the base soil is correctly adjusted and leveled with a straight edge, the removed sod is carefully laid back into its original position. Ensure the roots of the sod make firm contact with the new soil base to encourage re-establishment. Pressing the sod down with a roller or a flat board helps eliminate air pockets and ensures a seamless transition with the surrounding turf.
Post-Leveling Recovery and Maintenance
Immediate and consistent watering is essential for the recovery of the lawn, especially after the sod-cutting method. The newly leveled areas, whether topdressed or patched with lifted sod, must be kept consistently moist for the next two to three weeks to prevent the new soil from drying out and the grass roots from dying back. Deep, infrequent watering is preferred once the initial establishment period is over.
Restricting foot traffic on the repaired areas for a few weeks allows the grass to anchor itself firmly into the new soil. Mowing should be postponed until the grass has grown sufficiently, typically reaching a height of about three inches, and a sharp blade should be used for the first cut to minimize stress. Any thin spots in the topdressed areas can be overseeded to promote a dense cover, which helps prevent future erosion.