To choose the best grass seed fertilizer, gardeners should purchase the product that contains the best balance of chemical nutrients for their specific lawn needs. Fertilizers which contain high amounts of phorphorus are ideal for new lawns which are growing grass for the very first time. Fertilizers with an equal amount of nitrogen and phosphorus may be more beneficial for overseeding projects in which grass has already been established, but needs to be thickened and filled in.
All fertilizers generally consist of nitrogen, phosphorus, and potassium. Each bag is labeled with a three number ratio that tells consumers how much of each element is contained in the mixture respectively. Different fertilizers are recommended depending on whether a new lawn is being seeded for the first time, or whether an existing lawn is being overseeded to thicken it and fill in bare patches.
Consumers who are seeding a new lawn should purchase a grass seed fertilizer with two to three times the amount of phosphorus as nitrogen or potassium. This element is essential for the encouragement thick, healthy root growth. Phosphorus and potassium target the newly forming roots of the grass seeds and encourage them to spread and penetrate deep into the soil, often as far as six feet (1.8 meters) below ground. This allows the roots to tap into the below ground water supply of the land and maintain a healthy lawn year round. The product may be introduced to the lawn before or after applying seed by using a broadcast spreader.
Gardeners who are overseeding and covering bare spots may wish to use a fertilizer with equal parts nitrogen and phosphorus. Nitrogen is necessary for the growth and health of the top grass blades. A grass seed fertilizer with high amounts of both of these elements will work to establish the root system of the new seeds while also feeding the existing grass and encouraging it to flourish. As the current lawn grows, it will create protection for the germinating seedlings from birds and weather elements, and also crowd out invading weeds.
Some grass seed fertilizer bags may be labeled for use as a starter product. These bags combine lightweight mulch with the plant food nutrients that are found in other fertilizers. The mulch is mixed in with the feeding pellets and designed to rest on the surface of the soil and absorb moisture. The water is then released slowly over time amidst the germinating seeds, which do require daily waterings while becoming established. While inclusion of this type of mulching product with a fertilizer can be beneficial to gardeners, it is not strictly necessary to foster a lush and healthy lawn, and proper lawn care can eliminate the need for this additional ingredient.