Shut Up and Dig

Ta da! Welcome to 6a


Now that the controversy of Scotts and the NWF has come to a more or less satisfactory close, let us turn to the newly released USDA zone map. It may not be as scorching a topic, but I think it has plenty of interest—especially since this map has been so long in the making.

I remember nurseryman Tony Avent talking about the new zone map when I interviewed him in 2007.  Back then, it seemed like it was almost ready to announce. First Avent talked about the botched zone redo of 2003: "That map was not accurate. It got rid of half the zones [the a's and b's]. It was easier to use, but it was wrong. Chicago would have been zone 6." After that first map (which Avent says was created by a consultant the USDA sent off to make a map so he'd "stop bugging them"), the UDSA called together a new committee (of which Avent is a member), and decided on a 30-year average of temps rather than a 20-year average, which would have created too dramatic a shift. An early plan to have a, b, and c zone gradations rather than just a and b was put off for a future revision.

And now, more than five years after we had that conversation, the map he was discussing is finally out. What took so long? The process was a comedy of errors in many ways, according to Avent—read the whole story on his website—but basically they had to go back to the drawing board a couple of times. They’re happy with the results, despite the delays, because the new map is much more functional than previous versions, as well as incorporating the subtle a and be gradations. Their map has all the pretty colors we’ve come to expect, but this time it’s clickable; you can zoom in on your area to get a better look at the color gradation to figure out exactly where you fall, you can check by zip code, and there's more data available however you check.

There’s also already criticism. I have heard comments that the 30-year average was chosen to minimize the effects of global warming, and the USDA seems to have anticipated this with the following statement included in the map’s accompanying narrative:

Climate changes are usually based on trends in overall average temperatures recorded over 50-100 years. Because the USDA PHZM represents 30-year averages of what are essentially extreme weather events (the coldest temperature of the year), changes in zones are not reliable evidence of whether there has been global warming.

Others think the USDA doth protest too much. In a WaPo AP story, a Boston professor remarks, "“People who grow plants are well aware of the fact that temperatures have gotten more mild throughout the year, particularly in the winter time," and one of the creators of the 1990 map states "the latest version clearly shows warmer zones migrating north." Whether the map is reliable evidence of climate change or not, even its own narrow standard indicates that the coldest days are not as cold as they were. Which NOAA will officially confirm in July. It seems like the rabbit's out of the hat on this one.

FWIW, my zone did change. I have gone from 5b to 6a, which I checked by comparing this with the one on the National Gardening Association site—still the 1990 one. The Arbor Day map has me between 5-6. After a decade-plus of gardening, however, I generally choose plants based on what I think will happen to them on my property, often not even looking at the zone on the card. (When I do, it can be surprising; some nurseries have been selling zone 6 plants here for years.)

The thing is, there are so many things besides technical hardiness that have an impact on plant survival. I trust a good nursery (of which we have many) to sell what should survive in my locality. But I fret about too-damp soil, too much shade, root competition, and—of course— my own ineptitude. I deal out death with abandon, regardless of zone hardiness. Zone maps are not for the likes of us, really. They provide guidelines for gardeners just starting out, innocents who cherish hopes that the illiterate plant world pays any attention to rules, zones, and fine print.

I have to be honest. This confirmation that Buffalo is slightly balmier than was previously thought might lead to a few changes. I won't be planting palm trees, but maybe I won’t baby the macrophylla hydrangeas as much.

Have you played with this map yet? Has your garden moved, compliments of the USDA?

Posted by on January 30, 2012 at 5:00 am, in the category Shut Up and Dig.
Comments are off for this post

20 responses to “Ta da! Welcome to 6a”

  1. Jon says:

    After over 10 years of no statistically significant temperature increase that could possibly be attributed to man-made warming, after the thousands of emails from Climategate I and Climategate II showing collusion and corruption at the very top of the man-made warming collaborations, after the conclusion of the UN IPCC that natural influences on climate will dominate for the next 20 to 30 years and the complete and absolute failure of any model or calculation to be correct over 25 years…it is insane to continue to suggest that man-made carbon dioxide is warming the earth by anything but a miniscule unthreatening amount.

  2. Daedre says:

    I seem to be one of the few who has not changed zones. I’m still in 5b.

  3. Steve says:

    Wow, long time in the making. So glad this has come out. Yup, still in 9b. Thanks for sharing.


  4. shira says:

    We changed from 6a to 6b – so nothing really changes, I’m still delusional about what will survive here.

  5. UrsulaV says:

    My area was previously in a tiny little finger of 7a stuck in the middle of 7b, so I’m not surprised to get reassigned to 7b. Quite frankly, unless you’re trying to grow really tropical plants here, the limiting factor is August, not the occasional cold night.

  6. Kaviani says:

    I’m still a very unreliable 8b. Travis county is a very iffy spot that 3 different zones can seriously affect…I’ll continue to wing it and stick mainly with Texas-trialed cultivars and natives.

  7. Michelle says:

    Hmmm..being that I am in a suburb of Buffalo…I guess mine changed…

  8. Michaela says:

    In Spokane WA, I went from a 5b to a 6a. Because of lost plants I’ve been buying plants rated 4 and below the past few years, and I think I’ll stick to that!! Averages are averages and it seems my garden has a colder micro-climate.

  9. Monica Felt says:

    I wonder if this is any better than Sunset zone maps for western gardeners?? We have always relied on Sunset in the nursery industry here in California.

  10. Eliz. says:

    I think most in the west prefer Sunset. But growers use USDA–or at least the labels do–so Sunset users need to know USDA.

  11. Laura Bell says:

    Could never get a definitive answer before – 9A or 9B ? Seemed like I was right on the borderline. Now I know I’m in 9A, but it doesn’t seem right since avocados are supposed to grow in 9A, but I know better (my experience & that of friends). Meh. I’ll keep doing what I’ve been doing. It’s survival of the fittest in my garden anyway.

  12. KM says:

    This is pointless for California. The Sunset zone map is much better for us but my fathers garden in northern NJ switched from 6b to 7a.

  13. Thad says:

    Went for 7a to 7b … but couldn’t be more on the border without the color changing on our property!

  14. Jason says:

    Here in Chicago we are still 5b. I kind of expected to move to 6a, there are so many signs of the winters getting milder (though also snowier, if that’s a word). For instance, my snowdrops are about to bloom, something that has never happened before late February. And animals that used to hibernate no longer do so (I know because I’m trying to catch a raccoon that has moved in under my porch landing.)

  15. Under the old map, I lived in zone 6 and worked in zone 7. The new map painted all of Long Island as 7a — but based on my observations, the 6 and 7 designation seemed more accurate. I’ll keep planting the way I always have. Cheers!

  16. Pat says:

    I went from 5B to 6A. But for the past few years, based on the behavior/survival of my plants, I have been gardening as if I lived in zone 6. My recent success with borderline plants suggests that the shift “south” has been underway for some time.

  17. skr says:

    Since we havent seen any significant warming for a decade, wouldn’t going from a 2 decade average to a 3 decade average actually magnify the effects of global warming instead of reduce them? Instead of a warm decade and a cool decade you would be averaging 2 warm decades and 1 cool decade.

  18. tropaeolum says:

    I always wonder, how do nurseries use the USDA zones?

    What I mean to say is, do nurseries label plants zone 6 that can THRIVE in zone 6 (down to -10F)? Or do they label plants z. 6 that can survive one night -10?

    That is the information that would be more helpful to me as a gardener.

    As it is, I will continue to only plant perennials that are hardy to z. 4-5 as you never know when we’ll get a winter that drops to -12. I don’t want to lose all my plants due to one winter of freakishly cold temps.

  19. Robin says:

    I’m back in 4b, where I’ve been regardless of what the USDA thought. I do have warmer winters overall than 10-20 years ago but those periods of extreme cold, which is what the map covers, are enough to kill plants meant for zones 5 and up.

  20. greg draiss says:

    Totally ignores micro climates while suggesting all any non-gardener can just enter their zip code, buy something, it dies they blame the garden shop…………”I am in zone 6A after all”……….not telling the store the following……..low spot facing a blustery north west breeze at bottom of slop where cold air drains to.

    the TROLL