How Much Fertilizer Does Your Lawn Need?
Calculate the right amount of fertilizer by lawn size, grass type, and season. Avoid burning your lawn with too much.
Understanding N-P-K
The three numbers on fertilizer bags represent Nitrogen (N), Phosphorus (P), and Potassium (K) as percentages by weight. A 24-0-4 bag is 24% nitrogen, 0% phosphorus, 4% potassium. Nitrogen promotes leaf growth and green color. Phosphorus supports root development. Potassium improves stress tolerance and disease resistance. Most established lawns need primarily nitrogen — phosphorus is only needed for new seeding or sod.
Fertilizing Schedule
Cool-season lawns: Primary feeding in early fall (September) and late fall (October-November). Light feeding in late spring (May). Skip summer — grass is stressed and does not absorb nutrients well. Warm-season lawns: Primary feeding in late spring (May) and summer (June-August). Stop feeding 6 weeks before first frost.
Avoid Lawn Burn
Never apply more than 1 lb of nitrogen per 1,000 sq ft per application. Lawn burn (brown spots from over-fertilizing) is caused by excess nitrogen salts pulling moisture from grass roots. Water immediately after applying fertilizer to wash granules off blades and into the soil. Apply when rain is expected within 24-48 hours for best results.
The single most impactful lawn fertilizer application is the late fall "winterizer" — applied after the last mowing when the grass has stopped growing but before the ground freezes. This feeding builds root reserves that fuel a strong spring green-up without early spring fertilizer.
