Potential of winter kill for perennial plants

Curt Reese, Agronomy and Soil Scientist, WCROC

Jared Goplen, U of MN Extension Educator, Crops

April 2018

Each Minnesota winter is different from the next, which makes it difficult to determine the likelihood of winter kill for perennial plants.  A cold winter does not necessarily mean that we will have winter kill, and a warm winter does not mean that we will have less winter kill.  Let’s see what we can learn by looking back at some historical weather data.

Significant winter kill of perennial plants, winter cereals, and alfalfa was noted after the winter of 2016-2017.  November 2016 started out 10.2 F above average followed by a near normal December.  However, temperature fluctuations from extreme cold to warm temperatures occurred in December with a low temperature of -29 F on December 19th and a high of 37 F on December 6, 22, 23, and 26. Rainfall on December 26 totaled 0.36 inches, which caused pooling of water in low areas along with ice-sheeting.  January and February 2017 were considerably warmer than average with several multi-day thaws which may have caused plants to break dormancy.  In February 2017, there were 13 consecutive days with a high above 36 F.  Cooler weather followed each warm up.  Throughout the winter, snow cover was intermittent and never exceeded 8”.  This pattern of thawing and freezing was most likely responsible for the increased winter kill noted in the spring of 2017.

The winter of 2017-2018 was much different, starting out with near normal temperatures.  Temperatures in December 2017 ranged from 50 F on the 3rd to -24 F on December 31.  Below average temperatures generally continued through the end of February with only a few days above freezing.  Overall, February was 5.5 F below average.   March temperatures were about average at 27.5 F.  Along with cool temperatures, the winter of 2017-2018 has had little snow cover.  No significant snow cover was noted until February 23 when 6 inches were recorded on the ground.  Maximum snow depth was recorded on February 25 with 11 inches, and by March 16 the snow depth was reduced to less than 3 inches.  A total of 29 inches of snow was recorded from November 2017 to March 2018.

Top soil and subsoil moisture going into the spring of 2018 is near field capacity, largely due to a wet fall.  In August we received 9.92 inches of rain.  September and October precipitation was 2.01 and 1.05 inches above the average of 2.32 and 1.84 inches, respectively.  Little runoff occurred from the precipitation that melted during the winter months. 

Overall, the probability of winter kill in 2018 is likely above average due to the cold winter temperatures and lack of snow cover. Winter kill will hopefully not be as severe, however, since this winter did not experience the extreme thawing and freezing cycles as in the winter of 2016-2017.

More weather data available.