Cool-season grasses should be fertilized in May if they are on a sprinkler irrigation system.
Fertilize cool-season grasses in May, says K-State expert
Slow-release fertilizers will help lawn look great through summer
April 30, 2020
MANHATTAN, Kan. – As the calendar turns to May, homeowners hoping for a lush lawn should be making plans for one of the more important tasks of the season.
“May is an excellent time to fertilize such cool-season lawns as tall fescue and Kentucky bluegrass, if they will be irrigated throughout the summer,” said Ward Upham, a horticultural specialist with K-State Research and Extension.
If the lawn is not on a sprinkler system, he said, fertilizing in May is not recommended because the plant often goes through a period of summer dormancy because of drought.
“But for irrigated lawns, we suggest fertilizing in May because the springtime flush of growth in these grasses has tapered off, so the fertilizer you apply will be less likely to cause excessive shoots than if you had fertilized at a full rate in April,” Upham said.
Upham suggests that homeowners use slow-release, nitrogen fertilizers, which promote controlled growth throughout the summer.
“Relatively few fertilizer available to homeowners supply all of the nitrogen in a slowly-available form,” he said, “but one such product that is widely available is Milorganite. Others available in the retail market are cottonseed meal, alfalfa-based fertilizers and any other products derived from plants or animals.”
Upham noted one exception: bloodmeal. “Contrary to popular belief, the nitrogen supplied by bloodmeal is quickly available,” he said.
“These products are all examples of natural organic fertilizers,” Upham said. “They typically contain less than 10 percent nitrogen by weight, so compared to most synthetic fertilizers, more product must be applied to get the same amount of nitrogen.”
That does mean that the slow-release products are a little more expensive, he said.
Upham urges homeowners to follow label directions, but in general, you should plan to apply one pound of nitrogen per 1,000 square feet. “If the fertilizer is 6 percent nitrogen by weight, you will need to apply almost 17 pounds of fertilizer per 1,000 square feet,” he said.
Homeowners who would like to save money and instead apply quick-release fertilizers should plan to split the application into two doses – one-half pound of nitrogen, not fertilizer, per 1,000 square feet in May, and again in early June.
Upham and his colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticultural Newsletter with tips for keeping yards healthy and beautiful year-round. The newsletter is available to view online; interested persons can also subscribe to have it delivered by email each week.
Interested persons can also send their yard-related questions to Upham at wupham@ksu.edu.
