Impact of the Polar Vortex

During the last week of January, the air outside our little acre in Falcon Heights felt like a frigid -36 degrees. Yikes! Temperatures were historically low due to the polar vortex, a large pocket of extremely cold air that sits over the polar region during winter. Sometimes, due to a high pressure system in the Eastern or Western Pacific, this arctic blast gets pushed further south and hits some of the Northernmost regions of the U.S. The polar vortex is nothing new to meteorologists, but it started making headlines when it chilled Minnesotans in 2014. And, despite the misnomer “global warming,” the polar vortex’s southern pattern is linked to climate change.

So, how did this year’s polar vortex event affect our farmers? According to our Grower Support Specialist, David Van Eeckhout, the crops that are in for the most trouble are perennial crops, especially fruits. Perennial crops survive throughout the year and are harvested multiple times before they die — some examples include asparagus, rhubarb, and fruit trees. Many farmers who grow these crops, and cover crops like alfalfa, may see more winter kill this year than usual (as high as 25% loss), especially because snow cover was minimal during the polar vortex. Heavier snowpack is usually able to offer some protection from the cold air but the combination of minimal snow cover followed by a thaw and refreezing of the ground was a double whammy for many crops and we just won’t know what the effect is until spring.

Of course, different farms experience the effects of the cold in different ways. Farmers Erin and Ben of Open Hands Farm in Northfield were excited about the deep winter temps, which help kill pests on their farm. “As fruit and veggie growers we’re loving the cold for its bug-killing effects. Starting the spring with little or no insect pest populations is a huge boon. A few more days would have been even more thorough, but the way it was so warm until mid-January we were starting to get concerned about having a high percentage of winter [bug] survival, so we’re glad to be having some good deep cold. We didn’t have a lot of bugs going into this winter, but even a small population that wakes up here in April or May can become a major problem fast. “

Other farmers, like Becca Carlson at Seeds Farm, found joy in the cold for other reasons. “We have been having fun with it, grooming skate ski trails through the fields and hunkering in by the fire scouring seed catalogs!” says Becca. Check out her Instagram to see some photos of the ski trail action.

In addition to Ben and Becca, we spoke with newly retired UMN Climatologist, Mark Seeley on his thoughts about the Polar Vortex. He explained to us that the seven-county Twin Cities region (which is comprised of Anoka, Carver, Dakota, Hennepin, Ramsey, Scott and Washington counties) hadn’t seen temperatures of -28 degrees in 23 years. That’s a big problem for any landscape plants planted after 1996, especially the ones rated for zones 4 and 5a as they aren’t suited for temperatures below -25, making it very possible they could succumb to winter injury. Come spring you’ll have to monitor your plants for symptoms including branch die-back, failure to bud, and even plant death.

As for pests, Mark said that the cold will likely help with suppression of in Pine Bark Beetle and Emerald Ash Borer larvae, which is great for Minnesota’s trees. Alas, the mosquitos Minnesota is so well known for are adaptive little buggers — expect to see them return in May, once temps begin to reach the 50’s.

As always, no two weather events ever affect things in the same way and in addition to record-breaking cold, the record amount of snow that has fallen in February presents other challenges — like collapsing hoop houses. A hoop house that caves in under the weight of snow is problematic for many reasons, one being that many farmers use their hoop houses to start their seeds this time of year. Only time will tell how this harsh winter will challenge and change our growing season — if you believe that spring will ever come, that is!

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