Can I Fertilize My Fescue Grass in the Summer?

Dangers of Summer Application

While a wide range of nutrients comprise lawn fertilizer, the most abundant element is nitrogen, which results in increased leafy growth. If applied in a liquid form or at an improper dosage, the salts within fertilizer can burn fescue roots and foliage, causing browning. As soils naturally warm and dry out and summer heat builds, fescue naturally begins to slow growth and become dormant to survive. Encouraging lots of leaf growth increases the plant's need for deeper roots and more water uptake. If the summer soil is too dry and too warm, the fertilizer causes more harm to fescue than any short-term gain of brief growth-spurt or greening-up is worth.

While many people assume spring fertilization of fescue lawn is best, it's actually better to focus fertilizing during the fall months, according to the University of Minnesota Extension. Fertilizing the fescue lawn results in increased root and leaf growth, and applying fertilizer in spring causes a heightened need for mowing and watering. In fall, these issues are diminished with application of slow-release granular fertilizer products. From fall to spring, the fescue lawn naturally greens up, sprouts new plantlets, develops deeper and stronger roots. This in turn better prepares it to endure the winter and start greening up faster in spring.

As a cool-season grass, fescue is used as a permanent, long-term lawn grass only in U.S. Department of Agriculture plant hardiness zones 3 through 7 -- the cooler summer regions of the northern half of the United States. Farther south, fescue quickly dies out from the long hot summers. In USDA zones 6 and 7, fertilizing fescue is best done in September, November and early April. Farther north, fertilizing can be done in early May and again in late August. Fertilization in all zones should be avoided during the heart of summer.

The easiest way to provide nitrogen nutrients to a fescue lawn in summer is leaving mowing clippings to decompose. You don't want a thick thatch layer over the lawn to shade the grass, but the shredded clippings are rich in nitrogen and release them back into the soil. This natural recycling of plant tissues usually provides just enough nutrition to sustain fescue through summer. If excessive yellowing of the lawn occurs, even when the soil isn't dry, apply a light application of an iron fertilizer to bolster green color without adding any synthetic nitrogen products.