I suffered a severe bout of “zone envy” this past week on Cape Cod. Mounds of red roses and deeply blue hydrangeas tormented me, and the condition was exacerbated by repeated sightings of gigantic thickly flowering dogwoods. Why are their hydrangeas so blue and the other plants so floriferous? And did I see a large, mature Crape Myrtle?
The hardiness zone is valuable for determining whether plants are likely to survive winters throughout North America, and both gardeners and industry professionals should understand both their zones and microclimate factors.
I remember a long-ago master gardener convention, when my non-gardening mother – a good sport, taking notes for me – rushed out of a seminar to ask me with some urgency, “What ‘zone’ am I? Everyone is asking!”
I answered that Western New York is mostly considered to be U.S. Department of Agriculture (USDA) Hardiness Zone 5, with some milder areas along the lakes. Now I would add the explanation that the National Oceanic and Atmospheric Administration (NOAA) and the USDA have worked together to update the hardiness zones map from the previous version, issued in 1990, so that much of Western New York has been reclassified as Zone 6a.
That means that the average annual extreme minimum temperature over a 30-year period is minus 5 to minus 10 degrees in much of our region.
Now read that again: They average the lowest temperatures over 30 years. Averages don’t mean you never will see the winter temperature dip below minus 10 degrees.
The rest of the zone story: In Western New York, the so-called Northtowns and Buffalo are generally a bit milder than the Southtowns. East Aurora and Holland showed up on the new USDA map as Zone 5a (minus 15 to minus 20 degrees), while Eden earned a 5b rating (minus 10 to minus 15 degrees) You can look up your specific location at www.plantmaps.com/interactive.
Does that mean everybody in Amherst and Buffalo should rush out to plant species that are labeled for Zone 6? Of course not. Even industry professionals are inclined to be cautious and consider possible extremes.
As Ed Dore, CNLP, a respected WNY landscape professional, once said to me: In the landscape and nursery business, we want our customers to have a good experience – with plants that live a long time. Somebody in Orchard Park might insist upon a Zone 6 plant – say, a tender Japanese maple species – and it might do fine for 10 years, but then zap, there’s a week in winter that suddenly hits minus 15 with no snow cover, and it’s over.
Ed and other industry professionals, including many arborists, are quick to remind everyone that there is a lot to plant survival beyond temperature extremes – from correct planting and maintenance, to soil and microclimate.
Old Cape Cod’s advantage
Getting back to the Cape and my angst over blue hydrangeas, we have to remember some soil basics, starting with pH. Here at home, the good garden centers offer products that promise to “turn hydrangeas” blue – at least the kinds of hydrangeas with flowers that can turn blue or pink depending upon the soil acidity.
But what a job it is, to acidify soil that is naturally alkaline – as is the case in most of our region, especially the northern half of Erie County. You can plant the rhododendrons and hydrangeas in peat-y soil, and use soil acidifiers, until you are blue in the face, but you may still produce flowers that are more mauve than deep blue. Then test the soil in that part of Massachusetts – pH 5.5 or 6.0 – and you’ll see why those darned hydrangeas look like they were spray-painted, bluer than blue. And I had to laugh at the American Rhododendron Society’s listing of successful rhododendron (including azalea) species in that part of the world. Sigh.
Comparisons with other gardening locations teach other lessons, too, such as the importance of geography. Consider how a maritime climate (intimately affected by close water bodies) is different from an inland location. Cape Cod is a peninsula, with everything relatively close to water, so it is consistently more temperate (cooler in summer, warmer in winter) than many areas in a similar latitude. Buffalo is also comfortably temperate – with especially wonderful summers – but farther inland that temperate factor diminishes.
Putting geography and hardiness zones aside, microclimate is relevant everywhere one lives, making the whole difference in the health and survival of a mountain laurel or peach tree. In cozy courtyards and sheltered beds in Lackawanna as well as Brewster, Mass., some gardeners are surely tending their fruiting fig trees, and crape myrtles are sometimes surviving in Hamburg. But those success stories depend entirely on the gardener’s care and the luck of the location.
It’s all relative
On the day before leaving the Cape, I went to the largest garden center to browse the plants – what gardeners do on any trip anywhere. Of course I found something I had to take home, even while remaining skeptical. I questioned the horticulturist on board: “Begonia grandis – in the perennials department? Do you have any experience with it? Really hardy to Zone 6?” It was new to them, too, but it comes on good authority – as my research verified. I will let you know.
If it’s any comfort to those affected by Zone Envy, tourists come to Buffalo and get a case of it too. Deep Southerners can’t grow many perennials because their winter is inadequate, and humidity in the Carolinas produces fungus diseases that totally wreck many of our best plants. Talk with a gardener from Alaska or Maine, and you’ll feel really smug about your Zone 5 success stories – and you could mention modestly that you’ve been recently reclassified to 6! Then look outside at our lush, effusive gardens as July commences and know that it really is all relative and what we have here is not bad at all.
Sally Cunningham is a garden writer, lecturer and consultant.