When to Fertilize an Overseeded Lawn

Fertilizing Time

• The best time to apply fertilizer to an overseeded lawn is immediately after seeding, as recommended by Richard Duble in "Turfgrasses." This will help to reduce the chances of fertilizer burn to the seedlings that can occur if it's applied later.

Fertilizer Type

• Starter fertilizers are commonly used for newly seeded areas, as these have a higher content of phosphorus. Phosphorus is required in greater quantity in new lawn areas since the very young grass roots are not able to absorb enough phosphorus even if the soil already has sufficient levels of the nutrient. Use lighter applications of nitrogen for several weeks after the emergence of seedlings to promote thick, lush growth.

Fertilizer Rate

• The University of California Extension recommends using 1 lb. of phosphorus and 1 lb. of nitrogen for every 1,000 square feet of grass on overseeded areas. Once grass is established, the fertilizer rate is 4 to 6 lbs. of actual nitrogen for warm-season and cool-season grasses. Divide this amount into four equal portions through the year. Avoid using more than 1 lb. of actual nitrogen at each application for every 1,000 square feet, as excessive amounts can lead to fertilizer burn.

Fertilizer Suggestions

• For lawn areas in shaded sites, use half the recommended amount of nitrogen as compared to lawns in areas of sun. Excessive nitrogen in shade increases grass susceptibility to traffic damage and disease. Fertilize cool-season grasses minimally during the summer. In grasses growing in sandy soil, reduce the rate and increase the frequency of fertilizer as compared to lawns growing in clay soil.