Can I Fertilize in the Summer?

What You Need to Know

Summer fertilization has opposite correct answers depending on grass type: warm-season grasses peak in summer and need feeding, while cool-season grasses slow or go dormant and can be damaged by nitrogen. The right approach depends on your grass type, local climate, and current lawn condition.

Warm-season grasses, including Bermuda, Zoysia, St. Augustine, and Centipede, are actively growing during summer months. For these grass types, summer is actually the ideal fertilization window. Apply nitrogen-based fertilizer every six to eight weeks from late spring through early fall, following soil test recommendations for your specific lawn. These grasses metabolize nutrients most efficiently when soil temperatures are between 70 and 90 degrees Fahrenheit.

Cool-season grasses, such as Kentucky bluegrass, perennial ryegrass, and tall fescue, present a different challenge. These grasses enter a period of reduced growth or semi-dormancy during hot summer months. Heavy fertilization during this time forces growth that the grass cannot sustain, leading to shallow root development and increased susceptibility to disease, drought stress, and insect damage.

If you must fertilize cool-season grass in summer, use a slow-release or organic nitrogen source at a reduced rate, typically no more than 0.5 pounds of nitrogen per 1,000 square feet. This provides a gentle nutrient supply without pushing excessive top growth. Avoid quick-release synthetic fertilizers entirely during hot periods for cool-season lawns.

Timing within the summer day matters as well. Apply fertilizer in the early morning or late evening when temperatures are cooler. Avoid midday application when the sun is most intense, as fertilizer granules can heat up on leaf surfaces and intensify burn risk. Water immediately after application to wash granules off grass blades and into the soil.

Several conditions should cause you to delay summer fertilization regardless of grass type. If your area is experiencing a drought and water restrictions prevent adequate irrigation, postpone fertilizing until conditions improve. Applying fertilizer to drought-stressed turf almost always causes more harm than good. Similarly, if daytime temperatures consistently exceed 95 degrees Fahrenheit, wait for a cooler stretch before applying.

Soil moisture is another important consideration. Fertilize only when the soil is slightly moist, not bone dry or saturated. Dry soil cannot effectively absorb dissolved nutrients, while waterlogged soil may cause runoff and nutrient waste.

For summer fertilization, consider using products with added potassium, which strengthens cell walls and improves heat and drought tolerance. A fertilizer ratio like 15-0-15 or similar with equal nitrogen and potassium works well for summer applications. Avoid high-phosphorus products unless a soil test indicates a deficiency.

Finally, mowing practices complement summer fertilization. Raise your mowing height by half an inch to one inch during summer to shade the soil, retain moisture, and reduce heat stress. The combination of proper mowing height, appropriate fertilization, and consistent watering creates a resilient lawn that handles summer conditions well.