When establishing a new lawn, whether from seed or sod, the nutritional requirements are distinctly different from those of an established, mature turf. Mature grass primarily needs nitrogen for color and top growth, but new grass has a more specialized need. The goal is to rapidly develop a deep, robust root system that anchors the plant and allows it to absorb water and nutrients efficiently. This initial stage requires a particular nutrient blend to transition the new grass into a self-sufficient plant ready for long-term growth.
Why Starter Fertilizer is Essential
The specialized product for this initial stage is known as a starter fertilizer. It contains a specific ratio of the three primary macronutrients—Nitrogen (N), Phosphorus (P), and Potassium (K)—listed as the N-P-K ratio. Unlike fertilizers for established lawns, which are high in Nitrogen for leaf growth, starter fertilizers feature a proportionally higher concentration of Phosphorus (P).
Phosphorus is the nutrient responsible for energy transfer and, most importantly, vigorous root development. Establishing a dense network of roots is the most time-sensitive biological process for new grass, making a high-P formula necessary. A typical starter fertilizer ratio might be 10-20-10 or 12-24-12, where the middle number, representing Phosphorus, is the largest component.
Nitrogen (N) is still included, often in a quick-release form, to encourage initial greening and blade growth necessary for photosynthesis. Potassium (K) supports overall plant health, aiding in water regulation and bolstering resistance to environmental stresses and disease. Using a high-nitrogen lawn food is not recommended because the high salt content can “burn” the delicate new roots and it lacks the necessary Phosphorus concentration.
Applying Fertilizer Relative to Seeding or Sodding
For new grass grown from seed, the timing of the starter fertilizer application is centered on ensuring the nutrients are immediately available upon germination. It is best practice to apply the granular starter fertilizer to the prepared soil immediately before or while sowing the seed. This ensures that as the tiny new root, or radicle, emerges, it instantly encounters the Phosphorus it needs to begin rapid development.
Before application, prepare the soil by lightly tilling or raking the top layer. After spreading the fertilizer evenly using a broadcast or drop spreader, lightly rake the soil again. This incorporates the granules into the top inch of the seedbed, preventing wash away and positioning nutrients where the new roots will form.
When establishing a lawn with sod, the process focuses on preparing the subgrade soil before the turf is laid. Starter fertilizer should be applied to the newly graded, bare soil just before the sod is rolled out. This ensures that the cut roots on the underside of the sod have immediate access to the high-Phosphorus blend as they begin to knit into the underlying soil.
In both seeding and sodding, using a spreader ensures even coverage, which prevents patchy growth or localized over-application that can cause fertilizer burn. Following the application rate specified on the fertilizer bag for your square footage is essential. Once the fertilizer is spread, a light watering helps dissolve the granules and make the nutrients accessible to the roots.
Transitioning to a Regular Feeding Schedule
The initial application of starter fertilizer provides the necessary boost for the first four to eight weeks of growth. Once the new grass has successfully established its root system and you have mowed the lawn at least once or twice, the focus of fertilization must shift. The first mowing indicates the grass is established enough to handle the next stage of feeding.
The subsequent feeding, typically scheduled six to eight weeks after the initial application, should use a fertilizer with a higher Nitrogen content and a lower Phosphorus ratio. The plant’s primary need has transitioned from deep root establishment to vigorous leaf and blade production, or top growth. A formula with a higher proportion of Nitrogen, such as a 4-1-2 ratio, supports sustained growth and maintains the deep green color of the maturing turf.
Continuing to use a high-Phosphorus starter blend after establishment is generally unnecessary unless a soil test indicates a Phosphorus deficiency. Mature lawns require a maintenance fertilizer that supports ongoing health. The new schedule will then follow a pattern suitable for an established lawn, adjusting the fertilizer type based on the season and grass variety.