Renovating an Existing Lawn

Late summer to early fall is the best time to renovate cool season lawns. Warm season lawns are best renovated in late spring to early summer. Attempts to upgrade existing lawns when conditions are not optimum for establishment are difficult at best.

A thinning lawn indicates some underlying problem. Failure to identify and correct the problem can often lead to further lawn deterioration and the need for repeated renovation. Some of the major causes of turf deterioration include:

	*	Improper lawn management
	*	Unadapted lawn grasses
	*	Improper nutrient balance
	*	Excessive thatch buildup
	*	Disease, insect, or weed infestation
	*	Improper selection and timing of pesticides and fertilizers
	*	Excessive competition from trees
	*	Soil compaction from traffic

Trees cause a number of problems for turf. The light intensity is reduced, hence the lawn thins out. The humidity is higher so disease problems are more likely to develop. Turf has increased competition for water and nutrients. This results in a shallow rooted turf that is more susceptible to pest attacks and environmental stress.

Increase the mowing height in shady areas and decrease the amount of nitrogen fertilizer. Selectively prune tree limbs to increase the amount of sun light. Tree removal or the planting of a shade tolerant ground cover may become necessary.

Set your mower at a low setting, mow, and collect the clippings. Remove undesirable vegetation (dead grass, thatch, and weeds). This may not be necessary if a slit seeder is used. For small areas a rake or hoe is ideal. For large areas make several passes with a dethatcher (power raker, vertical mower). Both low mowing and dethatching reduce plant competition and enhance light penetration for good germination and fast establishment.

The seed must have good soil contact or the birds might be the only ones to benefit. In small bare spots, loosen the top 4 to 6 inches of the soil. Large areas are best prepared for seeding by using a piece of equipment (such as an aerator or coring machine) that brings small soil cores to the surface. Core in several directions, allow plugs to dry, and then pulverize the cores before seeding.

An alternative is to use a slit seeder to drill seeds into the soil. Dry, compacted soils, obstructions such as rocks and trees, and excessive slopes may limit the usefulness of a slit seeder.

Consumer Horticulture | Quick Reference