Garden zones creeping North (my weekly newspaper column)

[flowomo]

My weekly newspaper column, published today. Also available online at:
http://www.cumberlink.com/articles/2006/12/28/editorial/rich_lewis/lewis85.txt

(newspaper is in southcentral PA)

Warmer winters changing plant life
By Rich Lewis, December 28, 2006

With temperatures in the 50s for most of this month, the closest I came to a white Christmas this year was when I spilled a cup of flour while making raisin bread for our holiday dinner.

And as The Sentinel’s Linda Franz reported yesterday, forecasters say we’ve got at least two more weeks of this early-spring-like weather ahead of us.

Love them or hate them, these mild winters are an effect of the global warming trend that most scientists agree is under way. Whether it’s just part of a natural cycle, or the consequences of irresponsible human behavior, or some of both, the earth is warming and we can expect to see lots of unsettling changes.

For example, Cameron P. Wake, a professor at the Climate Change Research Center at the University of New Hampshire, told reporter Ann Raver of the New York Times last week that winter temperatures in the Northeast have increased an average of 4.3 degrees over the last 30 years.

One of the intriguing results of that rise was highlighted in an Associated Press article on Tuesday, which reported that the map of “hardiness zones” so beloved by gardeners has been dramatically redrawn.

For those who aren’t familiar, a hardiness zone describes a geographic area in which specific categories of plants can grow based on the minimum temperatures of the zone.

The zones are numbered 1 (the coldest) to 11 (warmest).

The zones were developed by the U.S. Department of Agriculture, but the department hasn’t updated its map since 1990. However, the National Arbor Day Foundation looked at the last 15 years of data collected from 5,000 National Climatic Data Center cooperative stations across the continental United States — and decided that the 1990 map was no longer right. So the foundation issued a revised map this month and it’s an eye-opener.

Northern Pennsylvania used to be entirely in Zone 5 and Southern Pennsylvania in Zone 6. But now, as you can see from the maps, the north is all in Zone 6 and a big chunk of southcentral Pennsylvania is now in Zone 7. In other words, Cumberland County now has the winters they used to have in the northern halves of Virginia, North Carolina, South Carolina, Georgia, Alabama and Mississippi. Those “southern” places have now moved up into Zone 8.



The left map is from 1990; the right is the updated version. Cooler temperatures are indicated by darker colors.

What this means is that you can now grow things in Carlisle that would have frozen to death here not long ago. And things that once thrived in our cold winters might not be so happy anymore.

I actually experienced this last winter when four clumps of flowering lantana survived the winter in my yard and rebloomed this summer. Those plants are not supposed to live year-round above North Carolina. I was so excited I actually e-mailed the Southern nursery where I bought them to tell about it.

I’m thrilled because I love lantana, though in the South it can become an uncontrollable pest. We’ll see what happens when it gets really comfortable here.

Also, I enjoyed some wonderful, fresh figs this fall — picked right off a backyard tree grown (and well protected) by a friend in Carlisle. Fig trees are hardy only in Zones 7-11.

Raver writes, “In central Maryland, warmer winters allow me to grow Southern magnolias and apricot trees, but more insects are wintering over, and weeds, like poison ivy and ragweed, seem far more aggressive.”

That area jumped from Zone 7 to 8.

Raver also knows about a fruit farm on Long Island harvesting from trees “that once would not have survived on the farm.” The owners have also put in a bunch of kiwi vines, which “would have been unheard of” at one time.

As for the nation’s capital, “You could say D.C. is the new North Carolina,” Bill McLaughlin, a curator at the U.S. Botanic Garden on the Mall, told the AP.

As a result, the AP reports, the crape myrtles are flourishing in the D.C. area — “It was something that I would never consider planting” years ago, horticulture specialist Chuck Schuster said. “But now they’re thriving.”

Cornell scientists and their colleagues at the University of Wisconsin found in 2004 that lilacs are blooming about four days earlier, and apples and grapes six to eight days earlier, than in 1965.

The lilacs might not mind, but the apple trees might protest, because they need a long, cold winter to set their buds properly.

And “species like the Colorado blue spruce, which is native to colder places, could feel the effects,” said Arbor Day Foundation spokesman Woodrow L. Nelson.

Yikes! It’s hard enough to give up dreaming of a White Christmas, but do we have to give up locally grown Christmas trees, too? I’m not sure I want to be stringing lights and hanging bulbs on lantana shrubs 10 years from now.

On the other hand, a big palm tree might look nice all decked out. The good ones grow only in Zones 8-11, so we’ll have to wait a while on that.

But maybe not a long while.

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Rich Lewis’ e-mail address is:

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[flowomo]

1. no interesting anecdotes to add to this?

I'd be interested in what's happening in your area. Here's the map showing the changes: