Uneven surfaces can be caused by freezing and thawing (which causes soil to heave), poor soil quality, lack of care or even worms, which leave your bumpy lawn with castings on the surface.
Levelling a lawn can be straightforward, though it requires the right materials and timing. The ideal time to fill gaps or uneven low spots is during vigorous growth, which occurs in spring and summer. Leaving this process to the last minute late results in soil being left on the lawn surface.
Repairing Shallow Indentations
These can be easily repaired by top dressing the affected area. The best top dressing is the same type of soil that is already under the lawn, meaning you should try to obtain similar soil from another garden bed on your property.
The next best option is free flowing clean sand, which allows water to continue to flow freely on the soil surface. However, using sand can be problematic if your lawn contains a lot of clay, which turns the soil into a hardened consistency that prevents good drainage. Sand also increases drought susceptibility, so it is important to know what the grass on your lawn can withstand. Creating a mix of sand and topsoil is generally a good option.
Either way, top dressing should be applied conservatively. A good way to go about it is to apply a little soil/sand mix to the area (around a centimetre or so), allow the lawn to repair for a few weeks, and then repeat the process as often as needed.
Fixing Deep Indentations In Lawns
Deeper indentations require a different method of levelling as the turf is unlikely to tolerate such a large amount of soil placed on top of the lawn, which will most likely kill the grass. The other result is that a layer of new grass and thatch will sit on top of a dead layer of lawn, which will reduce drainage and repel water or create a water trap. Either way, the result is an unhealthy lawn that will have problems in the future.
The best way to go is to use the lift and fill method, wherein you cut the affected area in a strip shape using a spade. You then dig 4-5cm underneath the soil and lift out the affected area. Clean fill or sand is then added to the soil and the lawn is replaced on top so that it is level with the rest of the yard. The repaired area requires frequent watering with fertiliser for the first few weeks to help re-establish the roots.
For more advice on lawn care and lawn maintenance, talk the experts at Glenview Turf.