Plant Grass Seed First or Fertilize?

By Home & Garden Last updated Tuesday, June/11/2024

Fertilizer

New grass seeds require adequate nutrient levels. The best way to ensure this is to complete a soil test and fertilize according to the results. This provides optimal conditions for the new seed. If a soil test is not possible, using a starter fertilizer should provide acceptable results. Fertilizer must be worked into the soil at least three weeks before seeding for best results. Applying a slow-release nitrogen fertilizer ensures adequate nutrient levels for a longer period while reducing the risk of chemical burns on established grass.

New seedlings need fertilizer applications as they grow to provide continued access to nutrients. When seedlings reach 2 inches in height, an additional 1 pound of nitrogen per 1,000 square feet should be added to the lawn. This causes faster growth of seedlings while improving the growth of established grass as well.

Fertilizer should be applied to the soil before seeding a new lawn as well. Cultivating the soil with a tiller, dethatcher or lawn rake causes good contact between seed and soil, a vital factor in seed germination. Applying an herbicide to the area before seeding keeps weeds from overtaking the lawn while grass seedlings remain small and vulnerable to invasion. This should be applied at least two weeks before seeding to ensure the herbicide does not result in poor germination of the grass seed.

Fertilizing and seeding in the fall give new seedlings the best opportunity to grow while they're not stressed by the summer heat. These practices also provide adequate time for roots to become well established before winter. Choosing a different type of grass seed than the one currently planted may prove necessary to protect against poor lawn growth in the future. Choose a species based on its tolerance of moisture and light availability, traffic and maintenance levels for your lawn. Seeding bare areas again early in the spring gives grass a second chance to grow before heat and weeds stress the lawn. Do not fertilize in the spring if you fertilized last fall. This causes excessive top growth and weak grass.