New USDA Map May Mean Earlier Planting In North

A new map from the USDA has some northern gardeners hoping to grow plants that used to be considered too fragile for cold weather zones. The hardiness zone chart is about a half zone warmer than the last one issued in 1990. The USDA says the changes are not due to global warming, but to more sophisticated mapping methods. Seed sellers and buyers say that, whatever the reason, the warmer temperatures expand possibilities for planting this spring.

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The U.S. Department of Agriculture has updated its map suggesting the best places for planting fruits and vegetables that are sensitive to frost. But one big change stands out. The coldest temperatures on this map are about five degrees warmer than they were on the old one. That's got growers and seed sellers planning for longer growing seasons and a bigger choice of crops.

Vermont Public Radio's Charlotte Albright gardens in Zone 4A.

CHARLOTTE ALBRIGHT, BYLINE: The old USDA map warned that temperatures in this part of northern Vermont could hit 30 below zero. The new map estimates cold snaps won't go lower than a balmy 25 below. And other variables, like proximity to water and elevation, can now turn a spot within a frigid pink zone to a more forgiving purple. For companies like High Mowing Seeds in rural Vermont, it opens an expanding market for a larger inventory.

Strolling through his Spartan but busy warehouse, owner Tom Stearns says he may also have to revise planting guidelines on his packages.

TOM STEARNS: Again, there will be varieties that we can include to some stores and some regions that otherwise would not have been the most appropriate variety for that region. And we're seeing more and more customers in the north wanting to grow things like okra.

ALBRIGHT: Stearns is even dreaming of growing peaches - pretty risky in this frigid zone close to the Canadian border. But Cornell University plant and soil scientist David Wolfe says the map also brings not so good news.

DR. DAVID WOLFE: First of all, some of the local favored garden species may not do so well in the new climate, and then, there's likely to be some new invasive weedy plants like kudzu, for example, or certain insect pests that people haven't seen before they're going to have to deal with.

ALBRIGHT: Wolfe predicts growing legions of home gardeners and small-scale growers will be on the front lines experimenting with species and trying out new ways to combat threats. After all, they have less to lose than agribusiness from taking risks. But he says even larger companies like Monsanto and Pioneer Seeds will probably change some of their business practices in response to the new map.

WOLFE: So something like a crop like canola, for example, something that could probably be, as the climate continues to change, habitable zone where that crop could do well will expand northward, so that would expand sales for a seed company.

ALBRIGHT: Wolfe sees the new USDA map as a harbinger of global warming. The USDA, however, is careful not to explain rising temperatures on its new map as proof that the whole planet is heating up.

KIM KAPLAN: It's not a matter of whether there is global climate change or not. It's just not the instrument you want to use to try it and prove it.

ALBRIGHT: USDA spokeswoman Kim Kaplan says the 1990 map was based on temperatures going back to the 1970s - a notoriously cold decade. And she says the methodology of that map cannot be compared with the new one. But whatever the reason for the new normal, as some growers call it, it's not news to a landscape designer and nursery owner in rural Vermont.

PETER LEBLANC: I like pushing the envelope when it comes to plant material.

ALBRIGHT: Tucked into his cozy kitchen on a gray, drizzly, unseasonably warm February morning, Peter LeBlanc says he's got a thriving 15-foot sycamore tree that according to even the new USDA map should be dead by now.

LEBLANC: It's been there for about seven years, and that sycamore is generally not seen in Zone 3-4. It's more of a four-five plant.

ALBRIGHT: That's why LeBlanc says he will refer to the new map spread out on his kitchen counter, but he won't be ruled by it. For NPR News, I'm Charlotte Albright in northern Vermont.

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