Since I don't have a greenhouse or room indoors to keep marginal plants alive when the temperatures fall, I've pretty much avoided growing things above my USDA Zone. But in the spring of 2017, I tried a little zonal denial by planting a beautiful Alstroemeria 'Inca Ice' and a Sarcococca 'Fragrant Valley.' Both of these are plants that typically need a zone warmer than where I live. But these varieties were both listed as hardy for my zone. Alas, they died along with a depressing number of older shrubs and trees in the winter of 2017/18 when we had extremely cold temperatures with little to no snow cover. In fact, our biggest snowfall last season happened in late April.
PHOTO: DEC. 15, 2017
When I look at the print garden catalogs that are now arriving in the mail, I always look to see what zones are listed at the end of a plant's description. When I go plant shopping online, I tend to click on all those special ways of digitally searching — like listings of new plants, rare plants or those that a nursery has hybridized themselves.
Now and then I look at what plants a nursery offers that are specifically appropriate for my USDA hardiness zone. When I used my Zone 5 as a search tool recently, I had a bit of a lightbulb moment. Something I've known for as long as I've gardened in Wisconsin was right there in front of me; I realized I had been seeing it but not really acknowledging it in recent years.
What I saw were the temperatures that go with a Zone 5 designation:
USDA Zone 5a: —20° to —15° degrees F.
USDA Zone 5b: —15° to —10° degrees F.
In reality, we recently woke up to a low temperature of -28° with a wind chill of -48°, significantly colder than the expected lows for Zone 5.
PHOTO: MARCH 2, 2017
According to the map, I live in Z5b. I have an urban garden which makes it a little more protected but I have been ignoring, if not denying, that very cold zonal truth. We've had multiple snowstorms since the Winter Solstice (Dec. 21). They've beautifully covered garden with a deep blanket of snow which I hope was enough to protect everything from the Polar Vortex temperatures we just went through. We had a few days were the temps went up into the mid-40s: a change of 70°almost overnight. Then back to snow and freezing rain and snow again.
Despite all of our talk about warmer weather as part of climate change, it is the drier winter with little snow cover and cold temps like we had last year that is deadly for gardens like mine. Rather than playing with Z6 plants, I should be thinking about Z4 or even Z3. Time to get real in the garden again. No more planting for hotter summers. It's the colder winters that I need to be thinking about when I go plant hunting from now on.
