What's in this guide
Understanding N-P-K: What the Numbers Mean
Every fertilizer bag shows three numbers — for example 32-0-10. These are the percentages by weight of Nitrogen, Phosphorus, and Potassium. Choosing the right N-P-K ratio for each season is as important as the timing.
Greens and grows the lawn. The most important nutrient for turf. Too much at once causes surge growth and increases disease risk. Use slow-release N in summer.
Builds roots and supports new grass establishment. Most established lawns don't need extra P — a soil test will confirm. Only add P when starting a new lawn or overseeding.
Improves stress tolerance — drought, heat, cold, and disease resistance. Important in fall to harden the lawn before winter. Look for a higher K ratio in fall fertilizers.
Spring: Balanced (20-5-10) or high-N (30-0-6) to green up. Summer (cool-season skip / warm-season active): Slow-release high-N (32-0-6) for warm-season only. Fall: High-K winterizer blend (22-0-14) to build root reserves and winter hardiness. Never a high-N fast-release product in fall — promotes soft growth that's frost-vulnerable.
Cool-Season Grass Fertilizer Schedule
Cool-season grasses (Kentucky Bluegrass, Tall Fescue, Fine Fescue, Perennial Ryegrass) grow most actively in spring and fall when temperatures are 60–75°F. Their fertilizer schedule follows this growth pattern — feed when growing, hold when dormant.
Apply a balanced or slightly high-N fertilizer as the lawn greens up. Use slow-release nitrogen to avoid surge growth. This is not the most important application — don't over-invest here. Wait until the grass has been mowed 2–3 times before applying.
N-P-K: 20-5-10 or 18-6-12Late spring is the best spring feeding window for cool-season grasses. Apply a higher-nitrogen product as growth is at its peak. Keep to slow-release to avoid excessive top growth. Do not fertilize after late June — summer heat stress begins.
N-P-K: 30-0-6 or 32-0-10Fall feeding is the single most important fertilizer application for cool-season lawns. Grass is growing roots, not blades. A high-K winterizer blend builds root reserves, improves cold hardiness, and fuels a stronger spring green-up. Never skip this application.
N-P-K: 22-0-14 or 24-0-12 (winterizer)Cool-season grasses go semi-dormant in summer heat and fully dormant in winter. Fertilizing during dormancy causes root burn, promotes disease-vulnerable soft growth, and wastes product. Hold all applications until September or the following April.
No fertilizer during these periodsWarm-Season Grass Fertilizer Schedule
Warm-season grasses (Bermuda, Zoysia, St. Augustine, Centipede, Bahia) grow most actively in summer heat (80–95°F) and go fully dormant and brown in winter. Their entire fertilizer schedule shifts to align with summer growth.
Wait until the lawn is at least 50% green before applying the first feed. Premature feeding of dormant warm-season grass is wasted or damaging. A balanced fertilizer at light rate to kick off the growing season.
N-P-K: 15-5-10 or 20-4-8 (balanced)Summer is the prime growth period for warm-season grasses. Apply high-nitrogen fertilizer every 6–8 weeks during this window. Use slow-release formulas to avoid excessive surge growth and reduce mowing frequency. Bermuda and St. Augustine are heavy feeders — apply at the higher end of the rate range.
N-P-K: 32-0-6 or 30-0-10 (high-N slow release)Stop fertilizing warm-season grasses 6–8 weeks before the first expected frost. Late nitrogen applications promote soft growth that's susceptible to cold damage. If applying a final feed, use a low-N, high-K product to improve winter hardiness without stimulating top growth.
N-P-K: 5-0-20 or 6-0-18 (low-N, high-K)Warm-season grasses are fully dormant in fall and winter. Fertilizing dormant grass causes root damage and promotes disease. No applications until the lawn is actively growing again in late spring. If you want winter colour, consider overseeding with ryegrass — but maintain separately.
No fertilizer during dormancyMonth-by-Month Lawn Fertilizer Calendar
Use this calendar as a quick reference. Cool-season (C) and warm-season (W) timings are noted where they differ. Canada timings run 2–4 weeks later than US timings for the same actions.
Cool-Season Grasses (Bluegrass, Fescue, Ryegrass)
Warm-Season Grasses (Bermuda, Zoysia, St. Augustine)
Fertilizer Schedule by Grass Type
Annual nitrogen requirements and feeding frequency vary significantly between grass types. Bermuda is a heavy feeder; centipede is very light. Apply more than the grass needs and you cause excess growth, thatch, and disease problems.
| Grass Type | Annual N (lbs/1000 sqft) | Feeds per Year | Best Spring N-P-K | Best Fall N-P-K |
|---|---|---|---|---|
| Kentucky Bluegrass | 3–4 lbs | 3 (spring ×2, fall ×1) | 30-0-6 | 22-0-14 (winterizer) |
| Tall Fescue | 2–3 lbs | 2–3 (spring ×1–2, fall ×1) | 24-0-8 | 22-0-12 (winterizer) |
| Fine Fescue | 1–2 lbs | 2 (light spring, fall) | 18-0-6 | 18-0-12 |
| Perennial Ryegrass | 3–4 lbs | 3 (spring ×2, fall ×1) | 30-0-6 | 22-0-14 |
| Bermuda Grass | 4–6 lbs | 4–5 (May–Aug, every 6–8 wks) | 32-0-6 | None (dormant) |
| Zoysia Grass | 2–3 lbs | 3 (late spring ×2, late summer ×1) | 24-0-8 | None (dormant) |
| St. Augustine | 4–6 lbs | 4–5 (May–Aug, every 6–8 wks) | 30-0-6 | None (dormant) |
| Centipede Grass | 1–2 lbs | 1–2 (light summer feeds only) | 15-0-5 (low rate) | None (dormant) |
Centipede is the lightest feeder of all common grasses. Over-fertilizing centipede causes "centipede decline" — a difficult-to-reverse condition where the grass thins and dies. Never exceed 2 lbs of nitrogen per 1,000 sqft per year on centipede. Use a fertilizer specifically formulated for centipede if available.
Canada-Specific Fertilizer Timing
Canadian lawns are almost exclusively cool-season grasses — Kentucky Bluegrass, Fescue, and Perennial Ryegrass dominate from BC to the Maritimes. The schedule is the same as the cool-season schedule above, but timing shifts 2–4 weeks later due to the shorter growing season.
| Application | US Timing | Canada (Prairie/Ontario) | Canada (BC/Maritimes) |
|---|---|---|---|
| First spring feed | Mid-March – April | Late April – May | April |
| Main spring feed | May | Late May – June | May |
| Fall feed (★ most important) | September | Late August – September | September |
| Winterizer | October | Late September – October | October |
| Last application cutoff | Mid-October | Early October | Mid-October |
In Manitoba, Saskatchewan, and Alberta, the growing season is 4–6 weeks shorter than in Ontario or BC. The fall fertilizer window narrows significantly — apply by late September at the latest, as ground frost can arrive in early October. Missing the fall feed in prairie provinces has a larger impact on spring recovery than in milder regions. See our complete lawn care guide for a full seasonal calendar.
How Much Fertilizer to Apply
The rate is always expressed as pounds of actual nitrogen (N) per 1,000 square feet — not pounds of fertilizer product. To calculate how much product to apply, divide the desired nitrogen rate by the N percentage on the bag.
| Fertilizer Product (N%) | For 0.5 lb N/1000 sqft | For 1 lb N/1000 sqft | Notes |
|---|---|---|---|
| 10-10-10 (10% N) | 5 lbs product | 10 lbs product | Balanced — good for new lawns |
| 20-5-10 (20% N) | 2.5 lbs product | 5 lbs product | Spring balanced feed |
| 30-0-6 (30% N) | 1.67 lbs product | 3.3 lbs product | High-N lawn booster |
| 32-0-10 (32% N) | 1.56 lbs product | 3.1 lbs product | Summer/spring cool-season |
| 22-0-14 (22% N) | 2.27 lbs product | 4.5 lbs product | Winterizer — high K |
Never apply more than 1 lb of actual nitrogen per 1,000 sqft in a single application with fast-release fertilizer. Exceeding this risks burning the lawn and causing surge growth. With slow-release fertilizers, you can apply up to 1.5 lbs per application safely. When in doubt, split the annual total into smaller applications — it's always better to apply less more often than to over-apply once.