Bumpy, rough, uneven lawns are annoying, difficult to mow, and potentially dangerous. Several factors contribute to bumpy lawns.
Many older, established lawns become rough and uneven over time as the turfgrass gradually thins. Sparse, thin lawns have less foliar growth and cushioning effect than thick, dense turfgrass. Thin lawns may be caused by poor maintenance, shade, insects, diseases, and other factors. The reestablishment of a healthy, thick turf would help to alleviate this problem. Bluegrass is generally the best grass for sunny areas, while the fine leaf fescues tolerate considerable shade. Tall fescue is also shade tolerant.
Freezing and thawing of the soil during late winter and early spring also contributes to the roughness of lawns. The repeated freezing and thawing lifts up or "heaves" the soil, causing the soil surface to become rough or bumpy.
Small castings left on the soil surface by earthworms also contribute to the roughness of lawns. While earthworms are partially responsible for the roughness of lawns, their activity improves the growing environment of the turfgrass plants. Earthworms improve the turfgrass environment by helping to decompose thatch. Their holes improve air and water movement in the soil. Earthworms also improve soil structure. The presence of a large number of earthworms in the yard and garden indicates fertile soils. The destruction of earthworms is not desirable nor feasible. Earthworms are beneficial and most pesticides registered for lawns and gardens will not kill earthworms.
Good lawn care practices can help to alleviate the problems associated with rough, bumpy lawns. An application of fertilizer in the spring should thicken the turf and make the bumps less noticeable. Best results can be obtained in late summer (late August to mid-September). Begin by core aerifying the lawn. Then power rake the area. The power raking will break down some of the bumps in the lawn and also break up the soil cores deposited by the core aerifier. Rake off any loose debris (thatch) brought up by the power rake. Then sow appropriate grass seed for the site. Rake the area with a leaf rake to work the seed into the soil. Finally, keep the soil surface moist to encourage germination. The lawn should be thicker and the surface less rough upon completion of these steps.
Rough, bumpy lawns should not be rolled with a heavy roller. While rolling the lawn will remove some of the roughness, it also damages the turf by compacting the soil. Compacted soil conditions reduce turfgrass vigor and may eventually lead to a thinner lawn.
Rough, bumpy lawns are annoying. Breaking down some of the bumps by power raking and developing a thick, healthy turf should help alleviate this problem. Destruction of the earthworms is not feasible or advisable.
This article originally appeared in the April 28, 1993 issue, p. 56.