New grass seed should be fertilized, but only with a specialized product. New grass seedlings have unique nutritional needs that differ significantly from an established lawn. Applying the correct fertilizer at the time of seeding gives the young plant the necessary boost to germinate successfully and build a strong, deep root system from the start. This initial feeding increases the success rate of the seeding project, leading to a denser, healthier turf.
The Necessity of Starter Fertilizer
Standard lawn fertilizers are generally formulated to support the leaf growth of mature grass, often containing a high percentage of nitrogen, which can easily burn and destroy delicate new seedlings. These products are unsuitable for new seed because their chemical composition is optimized for established root systems. The specialized product needed is called a Starter Fertilizer, which is intentionally blended to meet the requirements of newly germinating seeds.
A starter fertilizer’s NPK ratio is specifically adjusted for new growth. The second number, Phosphorus (P), is particularly higher in these blends, with common ratios like 12-24-8 or 10-18-10. Phosphorus is a fundamental element in plant metabolic processes, playing a direct role in energy transfer and cell structure formation.
For a new seedling, this high phosphorus content is necessary to promote robust root development, which is the plant’s primary focus during its early weeks. Since phosphorus does not move easily through the soil, applying it with the seed ensures the nutrient is immediately available to the tiny roots as they emerge. The nitrogen component in starter fertilizers is typically lower and often includes a quick-release source to encourage initial leaf growth without overwhelming the fragile plant.
Optimal Timing for Application
The ideal time to apply starter fertilizer is simultaneously with or immediately before spreading the grass seed. This combined approach ensures the necessary nutrients are already present in the soil layer where the seed will germinate and the roots will begin to grow. If applied just prior to seeding, the fertilizer can be lightly raked or tilled into the top few inches of soil to maximize its availability to the emerging roots.
Using a broadcast or drop spreader is recommended to achieve a uniform application of the granular fertilizer, preventing nutrient “hot spots” that could damage the young grass. After both the fertilizer and seed have been spread, the area must be kept consistently moist through frequent, light watering. This watering dissolves the fertilizer granules, allowing the nutrients to penetrate the soil and become accessible to the seed, which in turn activates the germination process.
It is important to avoid applying the starter fertilizer too late, as the young roots need the phosphorus right at the beginning of their growth phase. The combined effort of fertilization and consistent moisture creates the perfect environment for the seed to transition from dormancy to a developing seedling.
Post-Germination Feeding and Care
Once the grass has successfully germinated and the initial starter fertilizer has been depleted, the young lawn will require a second feeding to continue its establishment. This follow-up application is typically recommended about six to eight weeks after the initial seeding, or approximately four weeks after the new grass first appears. At this point, the young grass will benefit from another light application of a starter fertilizer or a regular, balanced lawn food, depending on the manufacturer’s directions.
The initial mowing of the new grass should occur when it reaches a height of about three to four inches, and only the top one-third of the blade should be removed. This mechanical action encourages the grass to tiller, which is the process of producing more shoots and ultimately leading to a thicker lawn. After this first mowing, the frequency of watering should gradually be reduced, but the duration should increase to encourage the roots to grow deeper into the soil in search of moisture.
A significant caution must be observed regarding “weed and feed” products, which contain herbicides that can kill or severely damage tender new grass. These products should be completely avoided until the new lawn has been mowed a minimum of three times, which usually translates to a waiting period of two to three months.