Professional-grade granular fertilizer and winterizer (step 4). Regain is an extra step/process done to the prills that lets the nitrogen be taken up by the plant as needed instead of a slow release. Winterizer is the most important step of the year for cool season grasses (Kentucky Bluegrass, Perennial Rye & Creeping Red Fescues). Apply a professional "winterizer" fertilizer with iron to strengthen turf health. Iron is essential for producing a strong root system to put your lawn to "sleep" for the winter and to give it that vibrant green for upcoming spring. It is important your lawn does not wake up "hungry" in the spring due to missing Step 4. Apply to lawn in late fall for maximum results. Regain is a stabilized nitrogen additive available in Spring Valley professional fertilizers. Regain provides the most advanced, continuous protection and stabilization of applied nitrogen, insuring a turf manager’s fertilizer investment against wasteful nitrogen loss. This fertilizer protects plant cells from winter damage and is the key to a beautiful lawn next spring! One 50 pound bag covers 12,500 square feet.