It has been some time since winter temperatures were cold enough to cause concern for injury to bermudagrass pastures and hay fields, but this winter’s weather is in that category. Cold injury to bermudagrass is hard to predict because soil moisture and snow cover interact with temperature to increase or reduce cold injury. In general, moist soil conditions during the cold temperature period reduces cold injury and dry soil conditions during extreme cold increases potential for cold injury. The water in moist soil tends to hold heat better than dry soil. Think of it this way – dry, cold conditions tend to freeze-dry plants and roots. The longer the cold, dry weather lasts the more potential for cold injury. Snow cover insulates the soil and protects plants from extreme temperature fluctuations. Conditions are very dry statewide and as of this writing, 50 counties are under burn bans. That along with the repeated cold temperatures plunges will likely cause cold injury to some bermudagrass fields.
Assessing cold injury can’t be done in the field until the bermudagrass begins breaking dormancy. Very cold-sensitive varieties may suffer complete winterkill whereas others may exhibit slower and later greenup than normal. This will increase weed pressure and reduce season-long yield. Low soil fertility increases cold injury potential especially low soil potassium levels. The relatively mild winters in the upper south over the past several years have allowed varieties of moderate freeze tolerance to escape injury that will occur with a cyclic return to more severe winter conditions. Fewer cold-tolerant seeded varieties are available than cold-tolerant sprigged varieties. Some of the best bermudagrass varieties grown along the Gulf Coast are prone to winterkill and winter injury in Arkansas.
Some cold sensitive varieties planted from seed include Arizona Common, Jackpot, and Giant. These are commonly included in seed blends to provide quicker cover and first year yield, but tend to winterkill over time leaving the more cold-tolerant variety of the blend. Giant bermudagrass is very cold sensitive and winter kills easily. Jackpot has shown poor cold-tolerance on several farms in north Arkansas. Common survives well in the southern half of Arkansas, but may likely show winter injury this spring across north Arkansas. The most common cold-tolerant seeded variety is Wrangler. It’s cold tolerance is on par with many of the cold-tolerant hybrids grown in north Arkansas. Other commonly grown seeded varieties with moderate cold-tolerance include Cheyenne, CD-90160, and KF-194. All three have lower cold tolerance than Wrangler, but have been grown successfully in north Arkansas. The two numbered varieties are used in many seed blends sold in recent years.