Patience is the key to determining damage or death of plants from February’s record-breaking cold temperatures. The country is divided into hardiness zones based on average extreme low temperature data, which is collected over time by the USDA. Most of Oklahoma is either in Hardiness Zone 6b, with an average annual minimum temperature of -5 to 0 degrees, or 7a, with an average minimum temperature of 0 to 5 degrees. Oklahoma County is considered Zone 7a.
Fortunately, when this cold front arrived, our soil temperatures had been above freezing and our soil moisture was sufficient, which kept the soil warmer. The snowfall also helped insulate the soil.
If a plant classified as Zone 7 experiences temperature below 0 degrees, it may receive damage or could inevitably die. However, it is possible that the plant may have little to no damage – it will simply take time to determine the outcome. Freeze damage can often be seen in black or brown leaves, but it is possible they will flush with new foliage in the spring. Some plants may look fine, but may not produce any new growth in the spring. Time will tell.
Stem splitting is the most common indicator of freeze damage. Dieback of terminal shoot growth also occurs. Both of these symptoms may already be visible, but it may be later in the spring months before the damage appears.
Once the damage is identified, prune away the stem damage until you can locate live, green tissue. New growth may result from this or the plant may die back further. There are some shrubs that may have died all the way to the ground. Pruning all the way above the ground is an option as some shrubs will come back from the roots and some will not.
Patience is key moving forward. We suggest waiting until late March to remove, plant, prune, or fertilize until better assessment of any damage can be made.
