"The map reflects what the plants have known for years."
January 25, 2012 9:00 PM   Subscribe

The USDA has released an updated version of its plant hardiness zone map. Based on low temperatures from 1976 to 2005, it puts most US locations into a slightly warmer planting zone. While many headlines link the overall changes with global warming, the map also reflects factors such as urban heat, prevailing winds, and the slope of the land. The Washington Post has an interactive graphic showing the old and new zones.
posted by pernoctalian (26 comments total) 24 users marked this as a favorite
Reality is a hoax.
posted by gerryblog at 9:02 PM on January 25, 2012 [4 favorites]

The current Canadian version, developed in 2000, is based on much older data (1961-90). I don't know when we'll get an update, but I do know that I was eating perfectly ripened tomatoes from my Toronto yard in mid-December 2011 (picked green and partially red in late November).
posted by maudlin at 9:19 PM on January 25, 2012

The Southwest appears to have cooled.
posted by Sys Rq at 9:29 PM on January 25, 2012 [1 favorite]

The Arbor Day Foundation did an independent update of their own in 2006:
The new map reflects that many areas have become warmer since 1990 when the last USDA hardiness zone map was published. Significant portions of many states have shifted at least one full hardiness zone. Much of Illinois, Indiana, and Ohio, for example, have shifted from Zone 5 to a warmer Zone 6. Some areas around the country have even warmed two full zones.

In response to requests for up-to-date information, the Arbor Day Foundation developed the new zones based on the most recent 15 years' data available from the [NOAA].... [The new map] is consistent with the consensus of climate scientists that global warming is underway. . Tree planting is among the positive actions that people can take to reverse the trend.

Completely anecdotally, I've observed a number of trees in my town that seem to be distressed, especially with crown die-off. This has recently been linked to climate change.
posted by dhartung at 9:39 PM on January 25, 2012 [2 favorites]

California has cooled considerably.
posted by Duffington at 9:45 PM on January 25, 2012 [1 favorite]

Don't confuse us with facts and science....!!!!
posted by HuronBob at 9:45 PM on January 25, 2012

How is it possible that Seattle is in the same zones as huge parts of Georgia and South Carolina? Last time I checked, Seattle didn't enjoy one billion degrees and one hojillion percent humidity in the summer.
posted by Cool Papa Bell at 9:53 PM on January 25, 2012

The zones are based on minimum temperatures, not maximum.
posted by maudlin at 9:56 PM on January 25, 2012 [5 favorites]

SCIENCE: It's getting hot in herre, so take off all your clothes!

PLANTS: I am getting so hot, I wanna take my clothes off!

posted by argonauta at 9:56 PM on January 25, 2012 [11 favorites]

Tamarisk trees for everyone!
posted by Burhanistan at 9:59 PM on January 25, 2012

Seems like there's a lot more local detail in the new zones. For example, if you look at the 2012 map, you can now see Vermont's Champlain Valley along the western side of the state, which gets milder weather than the central mountains of the Northeast Kingdom's forests. In Maine you can see that its a bit milder up to Bangor.
posted by maryr at 10:34 PM on January 25, 2012

Up to the mountains north of Bangor, I should say.
posted by maryr at 10:35 PM on January 25, 2012

Thanks for posting this; I spent a significant portion of last fall in a project relating to agriculture, and one of the questions we were facing was predictions using new temp/zone information based on the warming. It's great that they have released an updated map.
posted by LobsterMitten at 10:52 PM on January 25, 2012

Tamarisk trees for everyone!

But not everyone for Tamarisk trees:

Tamarisk has invaded almost all watercourses and other wetland habitats throughout the Southwest, taking over more than one million acres of wetland.

Tamarisk is distinguished by its feathery, needle-like leaves and numerous small, pink flowers at the ends of the branches. Up to 500,000 small, windblown seeds can be produced per plant.

The tamarisk is highly adapted to arid climates. It thrives in very saline and nutrient-poor soil. During the spring it can grow as much as one foot per month. It spreads readily by seed and by root, trunk, and branch sprouts.

Tamarisk can usually out-compete native plants for water. A single, large tamarisk can transpire up to 300 gallons of water per day. In many areas where watercourses are small or intermittent and tamarisk has taken hold, it can severely limit the available water, or even dry up a water source

Tamarisk can grow in salty soil because it can eliminate excess salt from the tips of its leaves. When the leaves are shed, this salt increases the salinity of the soil, further reducing the ability of native plants to compete. Because of its ability to spread, its hardiness, its high water consumption, and its tendency to increase the salinity of the soil around it, the tamarisk has often completely displaced native plants in wetland areas.

From a wildlife point of view, the tamarisk has little value and is usually considered detrimental to native animals. The leaves, twigs and seeds are extremely low in nutrients, and, as a result, very few insects or wildlife will use them. In one study along the lower Colorado River, tamarisk stands supported less than 1% of the winter bird life that would be found in a native plant stand. Because of the tamarisk's ability to eliminate competition and form single-species thickets, wildlife populations have dropped dramatically.

At White Sands National Monument, tamarisk has invaded many interdune areas, where water is near the surface, threatening to choke out native vegetation.

It also threatens the White Sands Pupfish, which naturally occurs only in a few springs and one stream in the Tularosa Basin. Tamarisk invasion now threatens to dry up this pupfish habitat.

Tamarisk is difficult to eradicate. It resprouts readily after cutting or burning. Research and many programs are now in place to reduce or eradicate tamarisk, and laws are being enacted to eliminate its sale and importation. At Death Valley National Park, it was found that, when tamarisk was eradicated and native species allowed to grow, water returned to wetland areas and wildlife again thrived.

Even though they are so much like us.
posted by jamjam at 10:54 PM on January 25, 2012 [4 favorites]

That Arbor Day link is great, and lets you see a nice graphic that shows just the changes in zones from 1990 to 2006. Spoiler: +1 zone (indicating average minimum temps rose by 5 degrees) in about half the country.
posted by LobsterMitten at 10:59 PM on January 25, 2012

Yes, I certainly wasn't advocating planting Tamarisks.
posted by Burhanistan at 11:26 PM on January 25, 2012

I didn't think you were advocating planting them in any way, shape, or form, and I'm sorry I gave that impression.

I saw my comment as an amplification of your interesting point that they will inherit much of the earth, though they are anything but meek.

Since they pull salts out of deep ground water and deposit them on the surface, I wonder if they could be used to concentrate lithium deposits
posted by jamjam at 11:47 PM on January 25, 2012

No worries! Just clarifying for the folks at home.
posted by Burhanistan at 12:08 AM on January 26, 2012

Does anyone know why so much of CA has apparently cooled?
posted by fshgrl at 12:25 AM on January 26, 2012 [1 favorite]

Cool Papa Bell: How is it possible that Seattle is in the same zones as huge parts of Georgia and South Carolina? Last time I checked, Seattle didn't enjoy one billion degrees and one hojillion percent humidity in the summer.

It's because hardiness maps are much more about minimum winter temperature than summer max. So...London, where I live, which is on the same latitude as frozen parts of Canada, is in hardiness zone 9a, whereas Atlanta is in zone 8. Very counterintuitively, due to the moderating effect of the Gulf Stream current and a maritime climate our winters our actually less severe than many parts of the Southern US, despite the latter being thousands of miles closer to the equator.

This means you can grow loads of subtropical plants in the UK, even if they tend to look really disappointed off in the "summer."
posted by rhymer at 1:09 AM on January 26, 2012 [2 favorites]

Where I live it's zone 3 and semi-arid. It amazes me that I can plant tulip bulbs and get a flowery surprise in the spring with no intervention. Of course I have to spend $50 on soil and the 50% of flowers that actually bloom are eventually destroyed by hail.
posted by Pruitt-Igoe at 1:56 AM on January 26, 2012

Still zone 5B for me. :(

I really need a tool that will tell me what I should be doing every week for the specific plants (or even cultivars) that I have. And isn't a pain to use.
posted by DU at 4:19 AM on January 26, 2012 [1 favorite]

One flaw in this hardiness scheme is it does not consider duration of cold, wind, and snow cover, all of which have substantial affects on plant hardiness. As an example, my location (south coastal New England) is indicated as zone 7a. And yes, it is correct in that it almost never falls below 0 F in my region (the typical winter night drops into the low 20's). And yes, I do grow southern magnolia, crape myrtle, fig, and other tender plants that are distinctly southern. And they do fairly well. But still, northern Alabama is said to be in the same zone. However that is somewhat misleading. Northern Alabama does not experience the same duration of cold as my location. And indeed the mean winter temperature in northern Alabama is higher. And often our coldest weather comes on strong NW winds from Canada. +2 with strong winds can kill a tender plant much quicker than +2 under calm conditions. This does limit my zone pushing and it does mean my southern plants don't thrive to the same extent that they would in northern Alabama. Or think of it this way. A location could drop to +1 F every night in winter and it would still be considered zone 7a. So I think a really clever person should develop a hardiness map that somehow captures these nuances.
posted by Seymour Zamboni at 4:21 AM on January 26, 2012 [2 favorites]

Seymour, those parts of Northern Alabama in 7a are mountain tops, i.e. the butt ends of the Cumberland Plateau in Jackson County and Lookout Mountain in Dekalb. The higher elevations account for the cooler temperatures.
posted by The 10th Regiment of Foot at 5:15 AM on January 26, 2012

I really need a tool that will tell me what I should be doing every week for the specific plants (or even cultivars) that I have. And isn't a pain to use. --- Otherwise known as "experience." There can never be any program, guide, or gizmo to tell you that, since it comes down to the microclimates and conditions of where you have planted your plants.

That said, I've tried a few things ...
growveg.com is a subscription based service that lets you plan your garden, and it will provide email alerts based on the plants you've chosen about when to sow them based on your zip code.
PlantSmart will help you try to figure out what to plant where. It's got a usb port, and once you've initialized it, you shove it into the ground where you want to start planting and let it sit there for a couple of days. It measures the sunlight, the moisture, the temperature, and even the soil nutrients, and gives you specific recommendations on what plants will do well in that location. I've used it, as well as given one as a gift, and both of us have had mixed results with it. My friend doesn't believe the results she gets, and has stopped using it. I've followed the advice, and even planted what the device suggested, and while the plants aren't dying, they're not thriving, but since it's only been one season, it may be too soon to judge.
The Week-by-Week Vegetable Garden's Handbook tells you what you should be doing, when. Once you know your last frost date, based on your zone, you can tailor the content to your own garden, including when you should start your seedlings, when you can safely move them outside, etc. (I bought this book too late in the season last year, but now is a perfect time to buy and implement it.)
posted by crunchland at 5:15 AM on January 26, 2012 [8 favorites]

I was really hoping (from a selfish point of view) to get out of zone 2b.

On the other hand, the boreal forest is noticibly struggling...

There's a really interesting article about climate change in Fairbanks (PDF); in addition to the winter minimums not being quite so cold, the length of the growing season has increased dramatically, primarily because the date of the last frost is earlier and the first frost is later (now reliably in May/September, respectively, as opposed to sometimes occurring in June and August).
posted by leahwrenn at 9:24 AM on January 26, 2012 [1 favorite]

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