Yes, you should apply a specific type of fertilizer just before or at the same time as the grass seed to ensure successful germination and establishment. New grass seedlings require immediate access to nutrients that support rapid root development, which the seed’s limited energy stores cannot provide. Applying the right product gives the vulnerable new plants the best possible start to develop into a healthy lawn. This initial feeding is a foundational step, distinct from the fertilization used on established turf.
The Essential Role of Starter Fertilizer
The fertilizer used for seeding must be a specialized product called starter fertilizer, formulated differently from standard lawn food. The difference lies primarily in the nutrient ratio, represented by Nitrogen (N), Phosphorus (P), and Potassium (K). Starter fertilizers have a high middle number, indicating a higher concentration of Phosphorus (P), often seen in ratios like 10-20-10 or 18-24-12.
Phosphorus drives energy transfer within the plant and is responsible for robust root growth and early establishment. Since new seedlings have shallow root systems, they require this nutrient to be highly available in the topsoil. Standard lawn fertilizers are unsuitable because they often contain little to no phosphorus, which is frequently restricted to prevent water pollution.
Potassium (K) strengthens the young grass’s ability to withstand environmental stress, such as drought and temperature fluctuations, and enhances disease resistance. The Nitrogen (N) component provides the initial boost for healthy green color and shoot development without forcing excessive top growth.
Optimal Timing for Application
The ideal time to apply starter fertilizer is just prior to or simultaneously with spreading the grass seed. This timing ensures essential nutrients are present when the seed germinates and its roots begin to emerge. If nutrients are not immediately available, seedling growth will stall, resulting in a weaker lawn.
Spread the starter fertilizer evenly across the prepared soil using a broadcast or drop spreader. After spreading the seed, lightly rake the area or use a roller to press the seed and fertilizer into the top quarter-inch of soil. Incorporating the granular fertilizer into the surface layer ensures it is accessible to the developing root zone and promotes good seed-to-soil contact.
A follow-up feeding is necessary once the new grass has fully germinated and been mowed a few times. This second application should occur around six to eight weeks after the initial application, or four to six weeks after the seedlings first appear. This schedule ensures the young grass has a continuous supply of nutrients to transition into established turf.
Key Products to Avoid When Seeding
When seeding a new lawn, avoid using products that contain pre-emergent herbicides. These herbicides create a chemical barrier in the topsoil that prevents all seeds, including grass seeds, from successfully germinating. They stop the young root and shoot from establishing, meaning your new grass seed will not sprout.
Also, be cautious with high-nitrogen, fast-release fertilizers not labeled as starter formulas. Fertilizers with a very high first number (Nitrogen) or a quick-release nitrogen source can cause “fertilizer burn.” The high salt content draws moisture away from tender new seedlings, causing them to dehydrate. To prevent overwhelming the young plants, limit nitrogen application to no more than one pound per 1,000 square feet.