Hort Q&A: How cold will affect lawns

Carla Smith, horticulture educator
Pottawatomie County Extension Service

Will this bitter cold spell affect my lawn?

Bermuda lawns can be susceptible to winter kill, but they are also pretty resilient. This recent weather event was unusually cold for us, even record breaking. So, lets take a look at what this can mean for our turf and lawns specifically. Winter kill is a general term, not a disease or pathogen, for when turf grass dies during the winter. Environmental factors are the main general reason.

The soil temperature is not necessarily the same as the air temperature. The soil temperature is a little warmer and more stable. If the grass was not cut extremely short, the canopy and the insulation of the snow cover also help insulate the crowns or growing points of the turf. This is another good reason to increase mowing height later in the season. Most of the crown and regenerative plant materials are in the upper two inches of the soil, possibly down to 4 inch depth in some cases.

In 2009-2010 winter, wet soils, heavy snow, and colder than normal temperatures increased winter kill of Bermuda grass. What did we learn from this event? The vertical shoots may be damaged or killed back, but the buds and growing points may re-grow. Many areas were damaged but were brought back by intensive management. This included re-sprigging, plugging, sodding, or seeding to help with the process.

Locations to watch are shorter cut grass areas, north facing slopes, heavy shaded areas, poorly drained areas, places of foot traffic and soil compaction. Inspection of stolons and rhizomes for firm stems with green, white, red or purple internodes are a good sign. Soft, mushy, brown or tan internodes are a bad sign. Once soil temperatures warm in the spring and grass begins to green up, we will know more. So by early May, we should have an idea of what we may be dealing with. It is very difficult to tell the difference between dormant and dead turf at this time of year.

Note Bermuda grass may be more sensitive to herbicides during green up under these conditions. You may want to consider holding off on preemergent applications this spring. These inhibit seed germination of weeds, but also can slow down the growth of runners (stolons/roots) our turf grass may need to recover, If your lawn is in good health, skipping one spray may be very helpful. You can always follow up with a post emergent later if needed, once the turf grass has greened up and is on its way to a good stand.

Fertility is important heading into cold weather. Soils that are healthy help our plants to bounce back better. After the event, we want to maintain soil nutrients, but not push growth too hard. Roots and new shoots have to develop before they can take off with a flush of new growth. A big dose of fertilizer may not be helpful. Refer to our OSU fact sheets for more information:

HLA-6420 for Lawn Management, L-441 for Bermuda Calendar, and L-442 for Cool Season Lawns, Soil Testing L-249. These can be found online at osufacts.okstate.edu

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