Active pets, playful kids and ageing turf all contribute to a thin, stressed lawn. Or growing conditions change, and a fast-growing ash tree now shades that sunny lawn seed blend. Whatever the reason for the weakened lawn, reseeding the lawn introduces new vitality into tired turf. The best time to reseed is not when garden centres push their spring sales, however.
As summer temperatures wane, so do germinating weeds. Crabgrass (Digitaria spp.) germination slows as the annual weed focuses on setting seed, and other warm-season weeds find the lawn turf regaining vigour. Reseeding in late summer or early autumn allows cool-season grasses to take advantage of the cooler weather, establishing root systems and blade growth before winter freezes set in. Reseed between mid-August and early September for a strong, thick lawn in spring.
If your schedule doesn't allow for autumn reseeding, you may renovate your lawn in spring as the soil warms. April to early May offers decent conditions for lawn growth. Weeds, weather and water may conspire against you, however, stressing the new lawn as summer heat and drought hit the new lawn. The same hot, dry conditions also encourage weed growth, and the weeds may soon overpower your emerging seedlings. If necessary, use a targeted pre-emergent herbicide, such as siduron.
Correct soil problems, such as compaction or thick thatch layers, before reseeding. Even fertile and loamy late summer soils are often dry and inhospitable to grass seed, as heat has dried the soil. Before reseeding, soak the area to a depth of 15 to 20 cm (6 to 8 inches). Hand-pull weeds or, if using a spray weed killer, wait two to four weeks after herbicide application to reseed. Don't seed areas treated recently with a pre-emergent, as some pre-emergents remain active in the soil for months.
Although it seems simple, some homeowners overlook a basic step when reseeding -- choosing the right seed. Reseeding small portions of a bluegrass lawn with a fescue mix creates uneven textures, and your lawn slowly becomes a patchwork quilt of turf species. Choose similar grass species or consider reseeding the entire lawn, introducing new turf grass suited to the conditions. In trafficked or highly visible areas, consider using sod to cover small patches, especially if renovating a lawn in summer.