December Turf Tips

Jeffrey Derr and Adam Nichols

Although temperatures have gotten cold, warm-season turf species are/or are going dormant, and tall fescue has slowed down its growth, there are still things to consider turf-wise this winter.  Now is a good time to do a soil test. If your soil has become too acidic (pH below 6.5), one can add lime this time of year.  A soil test will also give the current status of phosphorus and potassium in the soil, which will determine fertilizer needs in 2025. Now is not the time to fertilize warm-season grasses (bermudagrass, zoysia, St. Augustine, centipede).  One can apply fertilizer to tall fescue in December if needed amounts were not applied in the fall but lower rates are recommended due to its slower growth during this time of year. Fertilizer applications made during the winter need to be made with a nitrogen source that does not require microbial breakdown to make the nitrogen available to plants.  Suitable fertilizer products for winter applications to tall fescue are sources containing ammonium or nitrate nitrogen or isobutyidene diurea (IBDU). Fertilizer applications are not recommended during winter to warm-season turf species. 

Now is a good time to apply postemergence broadleaf herbicides for control of winter weeds like common chickweed, henbit, lawn burweed, speedwells, and vetch. It is better to treat these weeds when small compared to spring when these weeds are much larger and thus harder to control.  In tall fescue, consider a triclopyr-based product or a 3-way or 4-way product containing dicamba.  An ester formulation, such as Turflon Ester or Speedzone, will generally provide better control than amine formulations as they penetrate the waxy coating on weed leaves better than amine forms.  Esters pose less risk of off-site plant damage in winter as deciduous trees and shrubs have dropped their leaves and thus are less likely to be injured by drift.  Make sure that these broadleaf herbicides do not drift onto pansy, winter vegetables, and evergreen ornamentals, though. The 3-way and 4-way broadleaf herbicides can also  be used in bermudagrass and zoysia.  Atrazine for homeowners or Recognition plus Turflon Ester (commercial applicators) are options for postemergence broadleaf control in St. Augustine.

Emerged annual bluegrass will be a challenge for homeowners as there are no easy answers in tall fescue.  Commercial applicators will need to wait until spring when they can consider use of products such as Xonerate or Velocity.  In bermudagrass and zoysia, there are a number of selective options for annual bluegrass control (Revolver, Monument, Katana, Certainty) by commercial applicators.  These herbicides will also control annual and perennial ryegrass as well as other cool-season grass species. A special option in bermudagrass is dormant applications of glyphosate (Roundup, others).  This is probably best used in the month of January when bermudagrass is completely brown. Watering one week after application will lessen the potential for any turf injury. Later applications, when bermudagrass is starting to green up, pose a risk of injury.  We have researched the use of glufosinate (Finale, Cheetah Pro, others) in bermudagrass and zoysia, and found sometimes a greater potential for injury than with glyphosate during early greenup.  An option for annual bluegrass control in St. Augustine is atrazine.

One can get an early start on preemergence crabgrass control by applying a product such as prodiamine (Barricade, others) during the winter as cold weather limits breakdown by microorganisms. One generally will not see season-long control, as a second application will be needed in in late spring but it does buy one time if a firm has a lot of properties to treat. Applying a crabgrass preventer / fertilizer combination to tall fescue is not advised as the fertilizer rate may be too high when applying the recommended rate of the crabgrass preventer.  Another advantage of s crabgrass preventer application in winter is that it will control Japanese stiltgrass (Microstegium), which germinates earlier than crabgrass, sometimes in late February if warmer conditions occur.  

And finally, limit traffic over frost-covered tall fescue or other cool-season grasses to prevent injury to the blades.