I’m hearing lots of hammering now as I write this, a sound I’ve heard around our town for weeks now. It’s all due to roof repairs that are required by the hail storm we had back on August 24. The hail wrecked roofs all over Northfield and in nearby towns as well. I’ve heard estimates that 80 percent of the roofs in Northfield will have to be replaced. Ours is due to be redone in a couple of weeks, just in time for the arrival of winter, or so we hope.

We had a killing frost last week, with lows around 25 degrees - our strongest sign yet of the approaching winter. Many of our gardent plants died, with the notable exception of two species of late-flowering plants: Lindley’s asters and the remarkable false hollyhocks (of the genus Malva, I believe).

I’ve spent some time readying the house and yard for winter - turning off and draining the outdoor water faucet, heaping leaves on plants, cutting out frost-withered vegetation, washing windows. And now it’s snowing outside, as had been predicted! The poor roofers! I’ve heard that the crews from warm-weather regions have left, leaving only the Upper Midwesterners. Well, many of those I expect are Hispanic immigrants who are willing to call our region home.

I ask for blessings to all roofers working in cold conditions!

I’m pretty sure I’ve correctly identified that plant with yellow flowers that I described in my previous entry. It’s most likely birdsfoot trefoil (Lotus corniculatus). Here are three shots I took on Saturday, July 8, here in Northfield, Minnesota:

Read the rest of this entry »

We’ve been enjoying wonderful weather here in my corner of the Upper Midwest. After having some early oppressive heat in late May, with high temperatures in the 90s, things have cooled off into the 80s, with nights in the 50s or 60s. Early summer is a wonderful time. Read the rest of this entry »

As I write this on November 16, I’m looking out the window at a snow-covered yard. We’ve had our first snow of the season, and the temperature is about 22 degrees Fahrenheit, with a nasty wind making it feel much colder. The high will remain in the 20’s today, and tonight it’s supposed to get down to 6 degrees. It’s even cold inside. I’ve got the space heater blowing warm air on my legs, because cold air is leaking through our old windows, which I haven’t yet covered with plastic film.

Winter is here! I therefore shout, “Hooray!” And I promise you there is no irony.

Many Upper Midwesterners are already grumbling about the snow and ice and bad driving conditions. Most children and a few of us oldsters feel differently. Our 20-month-old daughter was fascinated by the snow this morning, and I find it brings back pleasant memories of winters past.

The arrival of winter follows a warmer-than-average fall in the Upper Midwest, which gave us sunny weather with highs in the 60’s until only a few days ago—well into November, that is. We also had a record run of frost-free weather. From March 26 to November 10—229 days—the Twin Cities did not have a “killer frost?? of 28 degrees or lower. The average number of frost-free days is 185.

Most of the plants in our small garden had already perished before November 10 because of occasional temperatures around freezing. However, one group of purple-flowered plants, which I was told are false hollyhocks, were still thriving. The carrots were still looking healthy as well, and the clematis was hanging on. Now even those plants will be done in by the weather.

For those of you who want advice on how to keep warm this winter, see two of my columns from last year, “Dressing for Winter,” Part 1 and Part 2. Also, stock up your vehicle with winter safety gear. In his book Restless Skies, Paul Douglas, my weather guru, recommends the following in your car:

• shovel
• first aid kit
• nonperishable food with can opener, if necessary
• flashlight with extra batteries
• candles and matches
• extra clothing, boots, sleeping bags, and/or blankets
• tire chains
• battery-operated radio with batteries
• empty coffee can to burn the candles or melt snow for water
• booster cables
• charged cell phone

If that’s not enough, another source recommends including road flares, a tow cable, sand, salt mix, a knife, and paper towels. AAA and other vendors sell winter travel kits. I’ve never carried anywhere near that much in my car, but I’ll try to be better prepared this year.

Finally, to remind us to respect Old Man Winter, here’s a tidbit from Mr. Douglas: extreme cold presents a greater danger, on average, than do lighting or extreme heat. The odds of being killed by extreme cold are 1 in 6,165, whereas the odds of being killed by extreme heat are 1 in 12,310 and 1 in 30,000 for lightning (Star Tribune, September 11, 2005). (The odds of dying from cold weather must be a lot higher in the Upper Midwest.) About 700 Americans die of hypothermia, or extreme cold, each year.

But I don’t mean to scare you away from winter. Really. See you out on the ski trails and sledding hills.

What a difference a week makes at this time of year. Last week our southern Minnesota landscape seemed barren, with few flowers blooming and the grass still dormant. This week the scene here in Northfield has changed greatly. Magnolia trees, forsythia bushes, and daffodils are blooming, and the grass has greened up with some recent rain. In our own garden, we have an encouraging number of tulips rising, though none have flowered yet. The trees are gradually beginning to come into leaf.

Of course, the threat of frost is still real through May in our area and into June for northern parts of the region, reminding us that cold temperatures are the major limiting factor for plant life in the Upper Midwest. Anything planted here now had better be truly hardy.

Most plants are sold with an indication of their “hardiness zones”–the areas in which they can survive. The most widely used zones are those developed by the U.S. Department of Agriculture (USDA). The USDA Plant Hardiness Zone Map is a thing of beauty and is also quite geographically instructive. It covers Canada and Mexico as well as the United States–a fact I appreciate, since it gets those of us in the U.S. out of our all too nationalistic mindset. Looking at such a map we can see patterns of climate that extend across national boundaries.

The plant hardiness zones are numbered one through eleven and are based on average annual minimum temperature. Why is annual minimum temperature so important? Because low temperature is a primary source of stress for plants. (See the “Hardiness Zone Details” page for a list of zones.) Zone 1, for example, has an average annual minimum temperature below ?50 F. In other words, on average its lowest temperature of the year (its annual minimum) is lower than ?50 F. Sitting for the most part on the northernmost edges of the continent, Zone 1 is truly arctic; it includes Fairbanks, Alaska and Resolute, Northwest Territories.

Each zone has an annual minimum temperature range ten degrees higher (F) than the last. So, Zone 2 has an average annual minimum temperature range between ?50 and ?40 F, Zone 3 is ?40 to ?30 F, etc. At the other end of the scale, Zone 11 has an average annual minimum temperature above 40 F–making it frost-free. In North America, that gentle climate exists only in Mexico. The same zone also covers most of the Hawaiian Islands.

Zones 2 through 10 are further subdivided into “a” and “b” ranges–2a, 2b, 3a, 3b, etc. These a and b designations represent ranges of 5 degrees F in the annual minimum temperature. Zone 2b, for example, has an average annual minimum that is five degrees warmer than Zone 2a. Zone 10b, which includes southern Florida, has an average annual minimum temperature ranging from 35 to 40 F. So it, like Zone 11, is frost-free.

What about the Upper Midwest? Looking at the map of the continent as a whole, you can see the cold, low-numbered blue zones reaching down from Canada into the U.S. The coldest zone that touches the lower 48 states is Zone 2b, which reaches only into northern Minnesota; its average annual minimum is ?45 to ?40 F.

Looking at the “North-Midwest US” hardiness zone map for a more close-up view, the mildest parts of the region are in southern Iowa and eastern Wisconsin, which are in Zones 5a and 5b. In Zone 5b, located around Milwaukee, the average annual minimum temperature is ?15 to ?10 F, 30 degrees warmer than the coldest parts of northern Minnesota. (Urban areas tend to be warmer.)

Jumping back to the continental map, we can get some idea of how the Upper Midwestern minimum temperatures compare to those in other parts of the continent. The coldest parts of northern Minnesota have lows that are on par with those on the southern shore of Hudson Bay, the central parts of Canada’s prairie provinces, parts of interior Alaska, and the southern portion of Baffin Island–the latter two being very northern places indeed. Those parts of the region in Zones 3 and 4 are comparable to northeastern Montana, southern Ontario and Quebec, northernmost New York state and northern New England. Finally, the warmest parts of the region share their zone–Zone 5–with states stretching from Nebraska and Kansas to Pennsylvania.

What we have here in the Upper Midwest, therefore, is a great deal of climatic diversity, and we must choose our plants carefully.

We are in that time of year when the snow has melted, the days are warmer, and the sun is higher in the sky, but the earth has not yet greened over. The grass is still dormant and yellowish. Buds are on the trees, but the landscape still looks raw with the mark of winter’s cold touch. The threat of frost is still real, and nature, wise with many years of experience, steps out gingerly into the new season.

It’s not the prettiest time of year in the Upper Midwest. While warmer places revel with riotous flowers, we wait patiently, content with a few brave crocuses.

My thoughts and eyes have turned to the modest garden plots in our small yard. We live in a townhouse and have a little space for gardening in a courtyard, along the front walk, and in the back. We inherited a garden when we moved here last summer, and if all goes well its hostas, morning glories, thyme, rosemary, hens and chicks, and other plants will come back. We added tulips and black-eyed susans last fall.

I have two regional gardening books to help me: Gardening in the Upper Midwest, by Leon C. Snyder (Univ. of Minnesota Press, 1978), borrowed from my parents; and The Minnesota Gardener’s Guide, by Melinda Myers (Cool Springs Press, 2001).

From these sources I’ve already learned that gardeners tell us a good deal about regional geography. They must be aware of their own climate and its suitability for various plants. For example, they need to know when to plant so that the frost does not kill new growth.

Here is what Leon Snyder writes about the Upper Midwestern climate:

“In the winter, the temperature can drop to -40? F or colder. In the summer, temperatures can climb to 100? F or higher. Not only does this area have extremes of temperature but it also has a fluctuating rainfall. Summer droughts are not uncommon. Generally, the rainfall decreases as one moves in a northwesterly direction. Average annual rainfall in our area ranges from about 28 inches in the southeast to about 16 inches in the northwest. Fortunately, most of this rainfall comes during the growing season.” (p. 3)

In her discussion of climate, Melinda Myers analyzes frost dates. The last spring frost is a crucial determinant of when a gardener can plant. The number of frost-free days (on average) is obtained by counting the number of days between the last spring frost and the first fall frost. “The frost-free season varies from 107 to 160 days in southern Minnesota,” Myers writes, “and from 90 to 120 days in the northern part of the state.”

That means the colder parts of northern Minnesota are only frost-free for one quarter to one third of the year–from early or mid-June to late August, according to the map in her book. Southern Minnesota, including the Twin Cities, is generally frost-free from early May to early October. No part of the state is frost-free, on average, more than half the year. Although a night that falls to 30? F might be followed only hours later by a high temperature in the 50’s or 60’s, the region is indeed cold. But we already knew that.

Next week: More on geography and gardening, including links to pretty maps.