The process of establishing a new lawn often begins with a simple question: which comes first, the grass seed or the fertilizer? Determining the correct order of application is crucial for success. The proper technique ensures the new grass seed receives the immediate nutritional support needed for successful germination and the establishment of a robust root system. Achieving a lush, healthy lawn depends on applying the right product at the right time.
Defining the Necessary Tool: Starter Fertilizer
The generic term “fertilizer” is not specific enough when planting new grass, because young seedlings require a distinct nutritional profile compared to established turf. The appropriate product for this stage is known as starter fertilizer. This specific formulation is engineered to maximize the success of new grass seed.
Starter fertilizer is characterized by a high concentration of phosphorus (P), represented by the middle number in the fertilizer’s N-P-K ratio. Phosphorus plays a direct role in energy transfer within the plant’s cells, which is crucial for cell division and growth. For new seedlings, this nutrient is paramount because it promotes the rapid and strong development of the root system. Common starter fertilizer ratios, for example, might be 10-20-10 or 18-24-12, where the middle number is notably elevated.
General-purpose fertilizers, in contrast, typically contain much lower phosphorus content, as established lawns primarily need nitrogen (N) for blade growth and green color. Using a standard, high-nitrogen fertilizer on new seeds can cause chemical burn on the delicate emerging shoots. It also fails to supply the necessary phosphorus for deep root growth. This specialized starter formula ensures the tender roots have the immediate fuel required for a powerful start.
The Step-by-Step Application Sequence
The grass seed and the starter fertilizer should be applied either concurrently or with the fertilizer immediately preceding the seed. The timing of both applications must be closely aligned so the nutrients are present when the seed begins to germinate. The process begins with preparing the soil by removing debris and lightly raking the surface to loosen the top quarter-inch of soil. This preparation ensures the seed and fertilizer make direct contact with the soil, which is necessary for moisture absorption and nutrient uptake.
The granular starter fertilizer should be spread over the prepared area using a broadcast or drop spreader, following the recommended application rate. Once the fertilizer is spread, the grass seed is applied immediately after. Use a crosshatch pattern—applying half the seed walking in one direction and the other half perpendicularly—to ensure uniform coverage. A final, very light raking helps incorporate the seed and fertilizer into the top layer of the soil, placing the high-phosphorus fertilizer in the root zone just as the new roots are forming.
The final step is the initial watering regimen. The seeded area must be kept consistently moist, but not soggy, to encourage germination. This usually requires light, frequent watering multiple times a day until the seedlings emerge (one to three weeks, depending on grass type). After emergence, the watering frequency can be reduced, but the duration should be increased to promote deeper root growth as the young grass establishes itself.
Hazards of Using Pre-Emergent Herbicides
A significant hazard to avoid during the seeding process involves using any product that contains pre-emergent herbicides, often found in “weed and feed” fertilizers. Pre-emergent herbicides are chemical agents designed to prevent all seeds from germinating by creating a barrier that stops cell division in the sprouting root. While effective at preventing weed seeds from growing, the chemical is non-selective.
Applying a pre-emergent herbicide will completely negate all seeding efforts, as the chemical cannot distinguish between weed seeds and valuable grass seeds. The product prevents the new grass seed from developing a root system, resulting in a total failure of the lawn establishment. If a pre-emergent has been applied, it is necessary to wait for a specific period, often 10 to 16 weeks, before attempting to seed. Always check product labels for the phrase “weed preventer” or “pre-emergent” and avoid them entirely when seeding.
Long-Term Feeding: Maintenance Fertilization
Once the new grass has successfully germinated and established itself, the nutritional needs of the lawn shift, requiring a transition away from starter fertilizer. The young grass needs a different type of feeding that supports blade growth and long-term health. This involves switching to a maintenance fertilizer that is higher in nitrogen for continued density and color.
The transition to a general, nitrogen-heavy maintenance fertilizer should occur approximately six to eight weeks after initial germination or after the new grass has been mowed for the second time. This timing ensures the root system, bolstered by the initial phosphorus, is sufficiently developed to absorb the new nutrients. Maintenance fertilizers typically feature a higher first number in the N-P-K ratio, such as a 20-5-10 blend. Applying high nitrogen too soon can force excessive top growth before the roots are ready, stressing the young plant. Waiting for this window ensures the lawn receives the correct nutrients for its current stage of development.