MaryAnne Spinner, Chicago Master Gardener

Winter has finally arrived in ?>Chicago, but it's a month late. Although December started out chilly, the average temperature for that entire month was an astonishing 43 degrees. 2006 went out with a whimper; on December 31^st the mercury registered 57 degrees Fahrenheit downtown, 26 degrees above average. We went out for dinner coat-less on New Years Eve, something we can't often do in April.

In fact, the unseasonable warmth continued into the first week of January, at which point I received a worried report from friends that their hostas were coming up. A quick check of our garden reassured me that our hostas had wisely decided to stay under their blanket of mulch. My relief was short-lived; however, when January 12^th rolled around and the temperature reached 51 degrees–and scores of daffodils stood three to four inches tall all over our front and back yards. Of course, winter showed up shortly thereafter, illustrating the concept of "nipping in the bud". Let us pray.

Global Warming?

As it turned out, Chicago was not the only unusually warm place in the country (or world) last month. 2006 turned out to be the warmest year in the contiguous 48 states since records have been kept. The average temperature last year was more than 2 degrees higher than the mean temperature for all U.S. winters in the previous century. It was also fractionally higher than 1998, the year which set the previous temperature record for the country. Winters of both years–2006 and 1998–averaged about 55 degrees across the country. Seven months of 2006 were much warmer than average, and last January was the warmest ever chronicled.

This past December in Europe was also improbably warm. Restaurant patrons dined al fresco in Rome, Bulgarians holidayed at the seashore, roses bloomed in France, and World Cup ski training was cancelled in the Austrian and Swiss Alps for lack of snow. Allergy sufferers worried about trees flowering and releasing pollen, birds started nesting in the Netherlands, and Swedish bears just started hibernating–two months late. Trees blossomed in London parks, the culmination of Britain's own warmest year on record.

The situation was–and still is–far worse in Australia, however. Oz is into its fifth year of drought, but this summer (remember the opposite hemisphere factor) the drought looks to be the worst in the 114 years since Australians have kept track. In fact, some are calling it the worst drought in 1,000 years; presumably tree rings back up this claim. The Australian agricultural sector is suffering badly, with harvests of key crops like wheat, barley, and canola expected to fall 60 percent this year. And as farmers' debt levels are climbing, so are their bankruptcy and suicide rates.

Reservoirs on Australia's central eastern coast are down to 14 percent of capacity, and draconian water restrictions have been put in place. During a vacation in Melbourne in 2002, we noted that all the fountains in public parks and gardens had been shut off. Now, after four more years of meager rains, citizens of that normally green city face fines of up to $335 if caught washing their cars, filling their swimming pools, or showing any other type of "obvious disregard" for the water restrictions. Australians are forbidden to water their gardens, unless they use so-called "gray water" recycled from their showers or laundry facilities.

Global freezing?

While greenhouse gases and El Nino were being blamed for the warm-up across so much of the world, last week California fell victim to a deep freeze that is having a devastating effect on its agricultural economy. After four consecutive nights of freezing temperatures, up to one billion dollars of the state's crops are said to have been destroyed. The most serious damage is to the citrus crop; as much as three-quarters of California citrus was damaged in the field, with farmers cutting into ice inside the fruit. That state is the leading producer of citrus in the United States, accounting for some 86 percent of lemons and 21 percent of oranges sold. According to growers, more than 70 percent of the state's oranges, lemons, and tangerines were still on the trees when the freeze hit. One citrus grower estimated that the cost of a supermarket orange could triple.

Other California crops were also seriously damaged by the freeze. Depending on orchard location across the state, from 25 to 40 percent of the avocado crop was destroyed. Strawberry fields along the coastal regions were mostly in ruin, and flowers that would have produced the next berry crop also were lost to the frost. Even farmers whose crops survived are feeling an economic pinch. For example, most of the flowers grown in the state for the cutting industry (think roses for Valentines Day) are grown under glass, and heating costs to protect the blossoms from the unusual cold have soared. And as farms experience crop losses, the agricultural labor market is facing a crisis, with labor leaders predicting that 12,000 field workers and packing house employees will be out of a job for the rest of this growing season.

California was not alone in the recently weird colder-than-normal weather department. Arizona was just hit with a rare snowstorm, dumping a foot of snow in the northern part of the state, three inches in Flagstaff, and 1- ½ inches in Tucson. It even snowed in downtown desert Phoenix. Southern New Mexico received nine inches of snow, and as for successive storms in Colorado...well, my niece living outside Denver has been snowed in with her two little girls for what probably seems–to her–an eternity.

Shifting Hardiness Zones

What are gardeners supposed to make of all this? Are we truly experiencing irreversible climate changes? In Chicago and in other cities of the North, if the weather is taking a decided turn for the south, what might that mean in terms of future plant choices?

One national horticultural organization believes that the warm-up is permanent. The National Arbor Day Foundation (www.arborday.org), whose mission is to "inspire people to plant, nurture, and celebrate trees", recently updated its Hardiness Zone Map. The Arbor Day map is probably not as widely known as the U.S. Department of Agriculture's Plant Hardiness Zone Map, or even the American Horticultural Society's Heat Zones. Functionally, it has been designed mostly as a guide for planting trees. Still, it is thought to be based on carefully vetted statistics, supported by data from 5,000 National Climatic Data Center cooperative stations across the continental United States, data that has been collected over a 15-year period.

The National Arbor Day Foundation's observations are that from 1990 to 2006, much of the United States has grown warmer, and this trend should, in the organization's opinion, affect which trees we should plant. According to the revised map, Chicago has moved up from Zone 5 to Zone 6. Although I would tend to describe my downtown lakefront climate as basically Zone 5, it still has significant pockets of Zone 4 (or else I have managed to kill a number of plants rated to Zone 5 for other reasons). I certainly can't recall ever having coaxed a Zone 6 plant through the winter outdoors.

To illustrate how significant a change a zone upgrade might be, recall the difference between USDA Zones 5 and 6. Zone 5A describes a locale where the average annual minimum temperature is from 15 to 20 degrees below zero. The average minimum temperature for Zone 5B is 10 to 15 below zero, for Zone 6A is 5 to 10 degrees below zero, and for Zone 6B the range extends from zero to 5 below. Thus, we are looking at a swing of up to 20 degrees from one end of Zone 5 to the other end of Zone 6, certainly enough to turn an imprudently planted shrub into freeze-dried compost.

It should be noted that the USDA itself sponsored a revised map of hardiness zones back in 2003, created in conjunction with the AHS. This map also showed a band of warmer weather creeping in our direction. However, shortly after its creation, the USDA rejected the controversial new map–apparently because it was thought to be based on insufficient data–but not until after the AHS had already printed the now-discredited map online and in its magazine. According to the Wall Street Journal, the USDA has said that it still plans to issue a new map, "but won't say when."

Although I have no quarrel with the Arbor Day findings, neither do I have the expertise to judge whose map is more correct–at any given moment–and thus I am personally wary of embracing their new guidelines as of yet. Since the Foundation is a not-for-profit organization with decidedly good intentions (last year alone it distributed 7.8 million trees to U.S. communities, and planted 500,000 trees in national forests), I do not doubt its motivations for the revision. I would be far more skeptical if national zone creep were being pushed by a large seed company or nursery as a marketing ploy. I'd be the first one in line for camellias if I thought Chicago was now firmly in the Zone 6 camp, much to some camellia grower's joy.

Still, area gardeners might want to take a look at the new map online and make their own decisions about accepting and acting on a larger zonal definition. It probably won't break the bank if you plant a few bulbs of marginal hardiness, but a big investment (like a tree...) should be approached with more care.

Download a Palm to Your Palm

How can we keep up with all this, especially when getting into a buying mode in the next few months? In a perfect world, local nurseries would sell only those plants which are appropriate for our climate–whatever that climate might be.

But what can we do in the real world of the local garden center, where plant tags are often incomplete, ambiguous, or just plain missing? With luck, the center's staff knows what hardiness zone applies, how much moisture and sun a plant needs, and any other relevant cultural information needed in order to make an informed buying decision. However, given the extent of inventory and the constant introduction of new plants, this is not always the case, even with the most dedicated staffers.

So for those of you out there with Pocket PC's and Palm PDA's, there is some good news: Dr. Tim Rhodus of Ohio State University has developed a series of plant profile web pages that can be downloaded to a hand-held device. Now you can troll the garden center with your own pint-size plant help desk–and if you have ever accessed OSU's online PlantFacts, then you know the excellent quality of that university's plant information. The new program for hand-helds is called the OSU Pocket Gardener and, best of all, is available for downloading free of charge.

The OSU Pocket Gardener files have been developed for both Windows and Mac users, and are accessible with or without photographs to accommodate your space limitations. An initial 190 pages of data are available, arranged in categories of Annuals, Bulbs, Grasses, Groundcovers, Perennials, Shrubs, Trees, and Vines, and more plant profiles are in the works. The actual programs are not installed on your PDA, just the HTML files, so installation is supposed to be easy and quick. For the free download, go to http://hcs.osu.edu/pocketgardener.

Although I've never before had a real need for a PDA, maybe that's what I'll ask for on my next birthday–that and some sunscreen for our new warmer weather.

Do you have a gardening question? Email the Extension's Electronic Plant Clinic at rwolford@uiuc.edu, and our Master Gardeners will be glad to assist you.