Cool-Season Grass Management Calendar
By Ron Honig
In an effort to help homeowners plan their lawn management procedures, K-State’s horticulture department has developed a calendar to follow for tips and reminders on cool-season lawn care.
The following suggestions are for cool-season grasses such as Kentucky bluegrass or tall fescue. Zoysiagrass, bermudagrass, and buffalograss are warm-season grasses and require a different maintenance regime.
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. Combination herbicides such as Trimec or Weed-B-Gon containing the active ingredients 2,4-D and dicamba work well.
April
Apply crabgrass preventer when redbud trees are in full bloom, usually about April 1st to the 15th. Crabgrass preventers containing the herbicides Dimension (dithiopyr) or Barricade (prodiamine) normally provide season-long control with a single application. 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 good, thick lawn is the best weed prevention and may be all that is needed.
May
Fertilize with a slow-release fertilizer if you water your lawn or if you normally receive enough rainfall that your turf doesn’t go drought-dormant during the summer. If there are broadleaf weeds, spot treat with a spray or use a fertilizer that includes a weed killer. Rain or irrigation within 24 hours of application will reduce effectiveness of the weed killer, but the fertilizer needs to be watered in. If you are using a product that has both fertilizer and weed killer, wait 24 hours after application before watering it in.
If grubs have been a problem in the past, apply a product containing imidacloprid or chlorantraniliprole during May or anytime from May through June for imidacloprid. These products work to prevent grub damage. If rainfall does not occur within 24 hours, irrigate with 1/4″ of water.
June through Mid-July
Apply a second round of crabgrass preventer by June 15 – unless you have used Dimension (dithiopyr) or Barricade (prodiamine) for the April application as those two will last all season. Again, remember to water it in.
Late-July through August
If you see grub damage, apply a grub killer that contains Dylox.
The insecticides 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 drops.
September
Fertilize with nitrogen around Labor Day. This is the most important fertilization of the year. Water in the fertilizer if rainfall does not occur.
November
Apply nitrogen fertilizer. This fertilizer is taken up by the roots but is not used until the following spring. Water in the 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. Follow the labeled use rate for all products.
