Here is a PowerPoint presentation I made to the American Rose Society, North Central Division convention in the Wisconsin Dells on September 13th of this year. Some of the presentation is a reprise of my March 2014 Blog: "What the Heck was Wrong with This Winter" http://jack-rosarian.blogspot.com/2014/03/what-heck-is-wrong-with-this-winter_5.html and my September 2013 blog: "Winter Protecting Your Roses" http://jack-rosarian.blogspot.com/2013/09/winter-protecting-your-roses.html
For the most part, the slides speak for themselves. However, where explanation and comments are needed, I will fill in with some of the remarks I made during the presentation.
So here we go....
This is a picture I took of my nicely winter-protected Earth Song bed on Christmas Day 2013, right after we had received 8 inches of new snow cover, thereby providing the best natural winter protection of all. Here in Minnesota, we seldom have to dream of a white Christmas!
But our winters are definitely getting warmer, as we shall see.
Below is my recently updated Minnesota climatology chart showing the Extreme Minimum Temperatures (EMT) for the last 53 years at MSP airport. This is the statistic the USDA uses to determine the cold zones. As you can see, the Twin Cities are no longer consistently in USDA Zone 4b. As a matter of fact, there have only been three nights in Zone 4 in the Twin Cities, since 1999! That hardly puts us in Zone 4 and, as you can see, the mathematically determined trend-line has an upward slope of about 25 radian degrees. If you project that trend-line off the right side of the chart, it would appear that the Twin Cities will begin to see more winters in zone 6 than in zone 4, within the next five years.
The most recent USDA charts were released in 2012, based on 1976-2005 data. In other words, their data, prepared for them by Oregon State University, was already seven years old when they released it and is currently nine years old. Those seven winters were some of the warmest ever recorded, which made the USDA data invalid when they released it.
Good enough for government work? Not in my opinion. We just have to think for ourselves, given the data shown below.
Note that for all of the cities shown below the winter of 2013-2014 was unusually cold, pushing them down into zones that they had not seen in several years. Cities like Chicago, Detroit, Indianapolis and St. Louis were especially hard hit, relative to the much warmer EMTs to which they had become accustomed in recent years. Look at Indianapolis, for example: the winter of 2012 had been zone 8 and 2013 had been zone 7, when the bottom fell out in 2014, dropping them to zone 5.
This is a much bigger swing than the Twin Cities experienced and, even though we experienced a near record number of nights below zero in 2014, most of them were in zones 6 and 5; not a huge variance.
Milwaukee is rated at zone 5b, but they have had only five EMTs in zone 5 since 1999. The rest of the years have been in zone 6 and zone 7; go figure.
Chicago, which was classified in zone 5 for many years, is now classified in zone 6, which is correct, but looking at the Milwaukee and Chicago maps together, it's hard to understand why Milwaukee, just a few miles north is not classified similarly, given the data of the last several years. Looking at the slopes of their respective trend lines (Milwaukee's is steeper), both cities will likely see many winters in zone 7 over the next several years.
Look at Indianapolis: going from zone 8 in 2012, to zone 7 in 2013, to zone 5 in 2014; a big surprise for gardeners there, who aren't accustomed to extensive winter protection.
Detroit, which has perennially been in zone 6 ( I grew up and lived there until age 37, and can't remember anything colder than -10) has had eight winters in zone 7 and one in zone 8 since 1999. They've had only five winters in zone 5 in the last 53 years, and last winter was one of them. This is a much bigger variance than seen in most other Midwest cities. The only thing we ever did to our roses, when I was growing up, was to rake some leaves on the beds. That sure didn't work last winter, when both Lakes Michigan and Huron froze all the way across.
Like Indianapolis, St. Louis' winters dropped two zones from 2012 to 2014; almost making it three zones to zone 5! Suffice to say that no one there was ready for that to happen last winter.
What happened was an incursion of the "polar vortex" a phenomenon that had never been seen in the U.S. to the extent that it was in 2014. Note, in the two graphics below, that unusually warm air, both to the west and east of North America formed a "pincers" around the normal polar vortex, a cyclone of super-cold air rotating tens of thousands of feet above the north pole (south pole too) tipping it over into central Canada and the Midwest USA. Note, in the second graphic below, that it also happened in China and eastern Siberia, which you would expect, but something that was not reported here.
Note that it was as warm in England and Western Europe (just to the right of Greenland on the great circle map below), on February 27th, as it was along the Gulf Coast of the United States; pretty amazing.
Be sure to also read my blog: "Winter Protecting Your Roses", written in September 2013: