Lawn renovation helps repair the damage caused by disease, drought, pest infestation and shade. The process can be as simple as seeding bare spots or as extensive as killing the existing lawn and replacing it with new grass, according to the University of Rhode Island Landscape Horticulture Program's Green Share Fact Sheet on General Lawn Maintenance and Renovation. Typically, a complete renovation is not necessary unless 25 percent of the lawn is bare or covered with persistent broadleaf weeds like crabgrass or dandelion.
Eliminate the factors that lead to recurring problems in the lawn. For instance, prune tree limbs to allow more light and rain to reach areas of thinning grass below the tree. Apply an herbicide to kill weeds that crowd out existing grass. Use a rake or vertical mower to break up the thatch that prevents fertilizer from entering the soil. The University of Minnesota Extension's Lawn Renovation says understanding the reasons for lawn failure helps bring attention to cultural practices like fertilizing and mowing.
Renovate cool-season grasses like Kentucky bluegrass and fescues from March to September, according to the Colorado State University Extension's Renovating the Home Lawn. Early fall renovation yields better results for cool season grasses because the seedlings receive more rainfall and face less weed competition. Not all warm-season grasses establish by seed. Renovate warm-season grasses that are capable of establishing by seed, such as buffalograss and blue grama, from April to July. Warm-season grasses need enough to time to establish to avoid winterkill. Avoid lawn renovation after the first frost.
Most lawn renovation involves overseeding, or spreading new grass seed over existing lawn, according to Paul Tukey's "The Organic Lawn Care Manual: A Natural, Low-Maintenance System for a Beautiful, Safe Lawn." The method introduces similar or improved, disease- or drought-resistant varieties to improve the lawn's appearance. It is important to identify the primary varieties already growing in the lawn, because some grasses mix better than others. For example, ryegrass and fine fescue work well with bluegrass, but they do not blend with buffalograss. Contact local extension agents for help identifying the grasses in an existing lawn.