The U.S. This was thought to be due, in part, to a response to warmer winters being experienced. However, this winter brought a new term — polar vortex — and with it extreme cold to the Midwest and Eastern states. Growers saw temperatures unlike they’d seen in 10 or 20 years.
Many cultivars thought to be grown successfully in the new hardiness zones could have sustained winter injury. And, with every temperature plunge into the sub-zero digits, the potential for winter injury increases. What complicated the matter was not just the temperature, but the duration of those extreme lows. The daily temperatures (warmer than normal) preceded the sudden drop, and the temperature fluctuation between freeze and thaw impacted the state of cold hardiness of plants at the time of exposure to extreme lows.
The extent of the damage, however, will depend on the variety planted.
To read the complete article click on the link below: