A comprehensive guide to properly fertilizing your lawn in spring based on grass type. This guide helps you determine the right timing, fertilizer type, and application methods for both warm-season and cool-season grasses to achieve a lush, healthy lawn throughout the growing season.
Garden Area
Coverage for average 5,000 sq ft lawn
Maintenance
Annual spring application
Sun Exposure
Full sun to partial shade
Water Requirements
Regular watering after application
Plant Types
Cool-season grassesWarm-season grassesKentucky bluegrassFescueBermudaZoysia
Materials Needed
- Based on product label (approximately 1 lb nitrogen per 1,000 sq ft) Nitrogen-rich lawn fertilizer (for cool-season grasses) (Look for slow-release fertilizers with an NPK ratio around 20-5-10)
- Based on product label (approximately 0.5 lb nitrogen per 1,000 sq ft) Balanced lawn fertilizer (for warm-season grasses) (Look for fertilizers with an NPK ratio around 16-4-8)
- 1 Soil thermometer (For monitoring soil temperature to determine application timing)
- 1 Broadcast spreader or drop spreader (For even application of granular fertilizers)
Steps
Timing for Cool-Season Grasses
- For cool-season grasses (Kentucky bluegrass, fescue, ryegrass), wait until soil temperatures consistently reach 55-60°F (13-15°C) at a 2-inch depth, typically in late spring after the first flush of growth.
- Avoid applying fertilizer too early when grass is focusing on root development rather than leaf growth.
- In northern regions, this typically falls between mid-April and early May, depending on your specific climate zone.
Explanation
Cool-season grasses experience two primary growth periods: one in spring and another in fall. Spring fertilization should be lighter than fall application because excessive spring nitrogen can lead to rapid top growth at the expense of root development, making the lawn less drought-resistant in summer. The timing is crucial—applying when soil has warmed sufficiently ensures the grass can effectively utilize the nutrients.
Pro Tips
If you applied fertilizer in late fall, reduce your spring application by about 25%. For lawns in shaded areas, wait an additional 1-2 weeks as these areas warm more slowly. Check your 10-day forecast to ensure you're not fertilizing right before a heavy rain that could wash away nutrients.
Timing for Warm-Season Grasses
- For warm-season grasses (Bermuda, Zoysia, St. Augustine, Centipede), wait until the grass is actively growing and has greened up at least 50% after winter dormancy.
- Soil temperatures should consistently reach 65-70°F (18-21°C) at a 4-inch depth.
- In southern regions, this typically falls between late April and mid-May.
Explanation
Warm-season grasses enter dormancy during winter months and resume growth when temperatures warm in spring. Fertilizing too early wastes nutrients and can contribute to weed growth since the dormant grass isn't actively taking up the fertilizer. The 50% green-up rule ensures the grass's root system is active enough to utilize the nutrients effectively.
Pro Tips
Perform a simple soil temperature check weekly starting in April. Use an inexpensive soil thermometer inserted to a 4-inch depth, checking in the morning for 3-4 consecutive days. For Centipede grass, which requires less nitrogen, reduce application rates by 30-50% from the manufacturer's recommendation.
Soil Testing and Fertilizer Selection
- Conduct a soil test 4-6 weeks before planned fertilization to determine pH and existing nutrient levels. Most county extension offices offer affordable soil testing services.
- For cool-season grasses, select a fertilizer with a higher nitrogen content (first number in the NPK ratio), preferably with some slow-release nitrogen.
- For warm-season grasses, choose a balanced fertilizer with equal or near-equal NPK numbers for the first application of the season.
- If soil test indicates specific deficiencies (like phosphorus or potassium), select a fertilizer formula that addresses these needs.
Explanation
Soil testing provides crucial information about your lawn's specific needs, preventing over-application of nutrients that can harm grass and waterways. Different grass types have different nutritional requirements: cool-season grasses typically need more nitrogen in spring, while warm-season grasses benefit from a more balanced nutrient profile as they emerge from dormancy. Slow-release nitrogen sources provide extended feeding without promoting excessive leaf growth.
Pro Tips
If you can't do a full soil test, at minimum test the pH, as this affects nutrient availability. Most turf grasses prefer a pH between 6.0-7.0. If your pH is outside this range, address this before fertilizing. Also consider using organic fertilizers, which release nutrients more slowly and improve soil structure over time.
Application Method
- Ensure the lawn is dry but the soil is moist (water 1-2 days before if necessary).
- Calibrate your spreader according to the fertilizer package instructions for your specific grass type.
- Apply fertilizer in a grid pattern—first moving north to south across the lawn, then east to west—to ensure even coverage.
- Water the lawn lightly after application (about 1/4 inch) to wash the fertilizer off grass blades and into the soil.
Explanation
Even application is critical for preventing fertilizer burn and ensuring the entire lawn receives proper nutrition. The grid pattern application technique helps achieve uniform coverage. Working with dry grass prevents fertilizer from sticking to blades, while moist soil helps the nutrients begin breaking down. The light irrigation after application moves nutrients to the root zone where they can be utilized by the grass.
Pro Tips
Never apply fertilizer to wet grass. Always clean your spreader thoroughly after use to prevent corrosion. To avoid missed spots or over-application, use half the recommended application rate and make two perpendicular passes across the lawn. For edges near sidewalks or driveways, use a drop spreader or apply by hand to prevent fertilizer runoff into waterways.
Follow-Up Care
- Avoid heavy irrigation for several days following application; light, frequent watering is better initially.
- Don't mow the lawn for at least 3 days after fertilizing.
- Monitor the lawn for any signs of fertilizer burn (yellowing or browning patches) and increase irrigation if detected.
- For cool-season grasses, plan a lighter follow-up application 6-8 weeks later if needed.
- For warm-season grasses, schedule the next application for mid-summer (typically 8-10 weeks later).
Explanation
Proper follow-up care ensures maximum nutrient absorption and prevents potential damage from fertilizer concentration. Avoiding immediate heavy irrigation prevents fertilizer runoff, while the waiting period before mowing allows the grass to begin metabolizing the nutrients. The different follow-up schedules reflect the growth patterns of different grass types, with warm-season grasses having higher nutrient needs during peak summer growth.
Pro Tips
Keep pets and children off the lawn for 24-48 hours after application. Mark your calendar for future fertilizer applications based on your grass type's growth cycle. If unexpected heavy rain occurs within 24 hours of application, you may need to reapply at a lower rate within a few weeks.
Troubleshooting
- Fertilizer burn (brown patches): This typically occurs from applying too much fertilizer or applying to wet grass/dry soil. Immediately water the affected areas thoroughly to dilute the fertilizer. For severe cases, you may need to rake out dead grass and reseed affected areas.
- Uneven growth (some areas growing faster than others): Usually indicates uneven fertilizer application. Adjust your spreader settings and application technique for future applications. For now, maintain regular mowing and monitor moisture levels in slower-growing areas.
- No visible improvement after 3 weeks: Several factors could be responsible. Check soil pH - if too acidic or alkaline, nutrients may be locked up. Consider soil compaction - aerate if necessary. Verify you used the correct fertilizer type for your grass species. Lastly, consider seasonal timing - extreme temperatures can limit efficacy.
- Excessive weed growth following fertilization: This often happens when fertilizing too early before grass is actively growing. The fertilizer feeds weeds instead. Apply a pre-emergent herbicide according to label directions (ensuring compatibility with your recent fertilization), and adjust your fertilization timing for next year.
- Grass becoming too tall too quickly: Usually from excessive nitrogen application. Increase mowing frequency temporarily but never remove more than 1/3 of the grass blade at once. For your next application, reduce nitrogen by 25-30% or choose a fertilizer with more slow-release nitrogen.
