Lawn calendar for cool-season grasses

 

K-State horticulture expert suggests maintenance regime for cool-season grasses

 

At a glance: K-State horticulture expert Cynthia Domenghini shares a month-by-month calendar for maintaining cool-season grasses in Kansas.

More information: Matt McKernan, hortsupport@ksu.edu

Related: K-State Horticulture Newsletter,

March 11, 2026

K-State Extension news service

MANHATTAN, Kan. — As lawns begin to turn green, controlling weeds and applying fertilizer is important, but only when timed correctly.

Cool-season grasses, such as tall fescue or Kentucky bluegrass, are among the most common cool-season grasses needing attention, said Kansas State University horticulture expert Matt McKernan, who shares the following maintenance calendar:

March

Spot treat broadleaf weeds, if necessary. Treat on a day that is 50 degrees or warmer. Rain or irrigation within 24 hours of application will reduce effectiveness. Avoid early spring fertilization, which may promote weed or disease issues.

April

Apply crabgrass preventer when redbud trees are in full bloom, usually in April. The preventer needs to be watered in before it will start to work. One-quarter inch of water will be enough to water in any of the products commonly available. Remember that a healthy, thick lawn is the best weed prevention.

May

Fertilize the lawn with a slow-release fertilizer if you plan to water your lawn during the summer or if you normally receive enough rainfall that your turf doesn’t go drought-dormant. Water in any fertilizer applied.

If there are broadleaf weeds, spot treat or use a fertilizer that includes a weed killer. Rain or irrigation within 24 hours of application will reduce effectiveness of most weed killers. If you are using a product that has both fertilizer and weed killer, wait 24 hours after application before watering in.

If grubs have been a problem in the past, apply a product containing chlorantraniliprole in May or a product containing imidacloprid anytime from May through June. These products work to prevent grub damage. If rainfall does not occur within 24 hours, irrigate with ¼ inch of water.

June through Mid-July

Apply second round of crabgrass preventer by June 15 – unless you have used Dimension (dithiopyr) or Barricade (prodiamine) for the April application. These two products normally provide season-long control with a single application. Remember to water it in.

Raise mowing height to upper end of the recommended range to increase drought tolerance of the lawn. Water only as needed to prevent wilt.

Late-July through August

If you see grub damage, apply a grub killer that contains Dylox. Imidacloprid and chlorantraniliprole are effective against young grubs but may not be effective on late instar grubs. The grub killer containing Dylox must be watered in within 24 hours or effectiveness decreases.

Make preparations to overseed thin turfgrass, or to plant a new lawn. Conduct a soil test, purchase certified weed free grass seed, and be prepared to plant new grass seed between late-August and mid-October.

September

Fertilize and core aerate around Labor Day. This is the most important fertilization of the year for a strong, healthy turfgrass. Water in the fertilizer if rainfall does not occur.

Plant new grass seed. If no new grass is being planted, consider applying a weed preventer to protect against winter weeds such as little barley, henbit, or chickweed. At least one-quarter inch of water maybe needed to activate the weed preventer.

November

Fertilize with a product high in Nitrogen. This fertilizer is taken up by the roots but is not used until the following spring, when it supports an earlier spring green up. Water in fertilizer.

Spray for broadleaf weeds even if they are small. Broadleaf weeds are much easier to control in the fall than in the spring. Try to spray on a day that is at least 50 degrees. Rain or irrigation within 24 hours reduces effectiveness. Use label rates for all products.

McKernan reminds homeowners that using best practices for turf management is the most effective way to manage their lawn.

“This includes watering only when needed and only applying as much as needed. Deep, infrequent watering is more efficient than frequent, shallow watering,” he said. “Excessive fertilizer does not equal a healthier lawn; Follow recommendations for lawn height when mowing.”

He also recommends getting the soil tested to determine nutrient levels. The best start to a healthy lawn is healthy soil.

“Wait to apply fertilizers until you know what your turfgrass needs. This step can save homeowners time and money,” McKernan said.

McKernan and his colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes and gardens.

Interested persons can subscribe to the newsletter, as well as send their garden and yard-related questions to hortsupport@ksu.edu, or contact your local K-State Extension office.

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K‑State Extension is a short name for the Kansas State University Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the wellbeing of Kansans. Supported by county, state, federal and private funds, the program has county extension offices statewide. Its headquarters is on the K‑State campus in Manhattan. For more information, visit www.ksre.ksu.edu. K-State Extension is an equal opportunity provider and employer.