Green-Up Lawn Food for Seeding and Sodding 12-18-8 is used when seeding, sodding, or over seeding. This product has a high amount of phosphorus to help build a strong root system and to produce new grass to become thicker and greener. Product closely contains about 1 percent of iron for deep greening, and has a slow release of 30 percent nitrogen. Product contains humates for better root development. You can apply it at any time you seed or sod, and feeds your lawn up to 2 months. Make sure to apply to a dry lawn before it rains or before you water. Do not apply this product if there is lack of rainfall, diseases or heat, or if the temperature is higher than 85 degrees.