In spring, an emerald-green expanse of cool-season turfgrass is a welcome reminder that winter is behind us. For many, that lush, green growth has an aesthetic appeal. For these reasons, it is tempting to promote such growth in lawns with fertilizer. However, we suggest resisting that temptation.
Applications of nitrogen fertilizer in spring or in summer can favor the growth of warm-season grasses (bermudagrass, crabgrass, nimblewill, etc.), helping them out-compete your cool-seasons grasses like tall fescue and Kentucky bluegrass. Plus, fertilizing in spring or summer can increase disease activity. The most serious threat occurring in cool-season grasses fertilized in spring/summer is brown patch of tall fescue. In addition, spring fertilization can interfere with good root development, setting the stage for stress-related problems later in summer, including root diseases and the need for more watering.
Thus, we suggest that normally it is best to avoid spring and summer fertilization. The exception would be if fertilizer was not applied the previous autumn. However, even in that case, we suggest using only very judicious amounts of fertilizer. Along these lines, weed-and-feed products should not be applied in spring for a pre-emergent herbicide treatment since these products also contain fertilizer.
More information on environmentally sound lawn management can be found in the Extension publication, Considering the Environment in the Maintenance of Your Kentucky Lawn (ID-222).
By Paul Vincelli, Extension Plant Pathologist, and Gregg Munshaw, Extension Turfgrass Agronomist