Fertilization
Fertilization supplies the three primary nutrients grass needs: nitrogen (N) for leaf growth and color, phosphorus (P) for root development, and potassium (K) for stress resistance. Timing fertilizer applications to match your grass's active growth cycle is more important than any specific product.
When to Fertilize
Primary application in fall (September–October). Light application in spring (April–May) is optional.
Begin after full green-up in late spring (May) and continue through summer (August). Stop 6–8 weeks before first expected frost.
50°F+ for cool-season; 65°F+ for warm-season
Fall is the most critical feeding for cool-season grasses. Roots continue growing after the top growth slows, storing energy for spring green-up.
Fertilization Schedule by Grass Type
Rates are lbs of actual nitrogen per 1,000 sq ft. All figures are per application unless noted as annual totals.
0.5 lb N in April–May
Avoid high-nitrogen products in spring — modest feeding only before summer stress
Skip
1–1.5 lb N in September; 0.5–1 lb N winterizer in October–November
Switch to a high-K winterizer for the late-fall application to build cold hardiness
0.5 lb N in April
Skip
Semi-dormant in heat; nitrogen now increases disease risk
1 lb N in September–October
Skip, or 0.25 lb N only if clearly pale or thin
Skip
0.5–1 lb N in September
0.5 lb N in April
Skip
1–1.5 lb N in September–October; split into two applications 4–6 weeks apart
1 lb N after full green-up in May
Use 16-4-8 instead if lawn is newly established or coming out of overseeding
0.75–1 lb N every 4–6 weeks through August
Slow-release nitrogen prevents surge growth and reduces disease risk in heat
Stop — no application after 6–8 weeks before first frost
0.5–1 lb N after full green-up in May
0.5 lb N in July only if growth has slowed noticeably
Stop — final application no later than mid-August
1 lb N in April–May after green-up
Add a separate iron sulfate application if yellowing is present — do not chase color with extra N
0.5–1 lb N every 6–8 weeks through August
Stop — final application 6–8 weeks before first frost
0.5–1 lb N in May–June after full green-up
Never use a fertilizer containing phosphorus unless a soil test confirms deficiency — excess P triggers iron chlorosis in centipede
Skip
Additional nitrogen causes centipede decline
Skip
0.5–1 lb N in April–May
0.5 lb N in July
0.25–0.5 lb N in early September if still actively growing
Skip if growth has already slowed heading into dormancy
Why It Matters
- ✓Nitrogen drives the deep green color and density that distinguishes a healthy lawn from a thin one
- ✓Properly timed potassium builds cold hardiness and drought resistance before stress periods
- ✓Feeding at the right time strengthens the grass to compete with weeds rather than feeding the weeds
- ✓Under-fertilized lawns thin over time, opening space for crabgrass, dandelions, and moss
How to Fertilize
- 1Test your soil every 2–3 years to understand your baseline nutrient levels before guessing at fertilizer formulas
- 2Choose slow-release nitrogen (polymer-coated urea or IBDU) for even feeding over 8–12 weeks with reduced burn risk
- 3Apply with a broadcast spreader for uniform coverage — always calibrate the spreader per the bag instructions
- 4Water in granular fertilizer within 24–48 hours to activate it and wash it off blades, preventing burn
- 5Apply at half-rate in two perpendicular passes for more uniform coverage on slopes and irregular shapes
Common Mistakes
Related Guides
Never miss a fertilization window
Lawn Schedule sends you a reminder before each treatment window — timed to your zip code and grass type, not a generic calendar.
Get my free schedule →