it has me in z6 ...

and that is nonsense... i can not grow any z6 plants .. period ...

and i am not going out to search for z6 plants.. now that the faithless gov-ment tells me so ...

gotta love bureaucrats ...

thanks for the link ....

ken

Still 6b for me....barely. But after last years -25F, even if it put me at 7b or 8a, I would not change what I plant.

BTW, noticed that Little Rock Arkansas went from 7a to 8a. And my hometown went from 7a to 7b, which is probable pretty close.

Arktrees

I went from 7a to 7b but we commonly get close to 0 once a winter especially in my valley. Though this year we may not make it below 15*. There will be no pond walking for me this winter it appears :(

I think we should have stayed 7a personally...

Thanks for posting this c2g!

John

No change for me. At least its been steady.

There are so many varibles that come into play its not even funny.

Bud vs.root hardiness on grafts, snow cover, valleys, tree cover, soil type, winds, exposure just to name a few that can effect survival during the winter. Temperature is just one element.

Looks like I've been bumped down to Z6b. We had -17 degrees last winter...crapemyrtles froze back to the ground...
hortster

Lake MI must stabilize temps by me. I haven't seen lower than -14 in the last 5 years. I hope that trend continues as I establish my plants.

Bureaucracy plays no part in the collection of data, if by that, you mean some shenanigans at play. The numbers don't lie. I'm pretty sure it's more to do with the variables, a la whaas. Cold-hardiness rating of one given location is only the beginning of understanding what will work in your spot.

Now during the Bush Jr. years....there was some political pressure to NOT release the new zone map, because it seemed to support global warming, and of course, little Georgey couldn't have that!

+oM

Went from 6b to 7a. Do notice that typical zone 7 plants (Southern magnolias, Crape Myrtles, etc.), have become much more commonplace compared to just a decade ago. Downside--seems like a lot more severe weather impacting growing conditions (wind, drought, freakish snows, flooding, and heat).

I just saw the new map in the Musser Forests catalog on-line. I'm still 6a like before. The coldest we've got here for the last decade is single digits, but not below 0 F. Hope it stays that way. My live oaks are looking good still, knock on wood.

7b for me, I think that's about what I figured. Regardless, I don't plan to do anything different. I usually plan stuff that is indigenous to this area anyway and annuals are annuals no matter what! ;)

Yep, the numbers don't lie. Adrian, MI is in low zone 6a (nearly 5). What can be grown, and, what should be attempted (with confidence) depends on much more than just hardiness zone info, BUT I'd bet a master gardener like Ken would do just fine with certain zone 6a perennials there. Personally, I'd probably stick with zone 5 trees in that location, unless I was feeling adventurous. Even though Adrian is likely to just get warmer, predicting weather pattern shifts (future locations of weather patterns) is not an easy task, and things could always change (at least a little) one way or other (not to mention an anomalous year).

I will say this, sort of in line with Ken's comments...a LOT of decisions and variables went into the production of that map. There was no single "right way" to present the data. So, even though I have absolutely no doubt that the "bureaucrats" (BTW, most of them weren't bureaucrats at all) tried their best to present an honest and accurate picture, the results are merely an abstract representation of the data that was determined to be relevant as a much depended-upon guide.

Nothing has changed for me, I'm still on the border of 8A/8B.

It's totally wrong for here, so either numbers lie or people manipulate/misread them. 30 year norms for my location show we are solidly zone 8b. If I were to assume that average lows were 20-25 F (9A) as the new map shows, I would have alot of dead plants in the spring (I do anyway). The minima during the last 5 winters have been: 17 F, 16 F, 13 F, 17 F, and 18 F all 8B and one 8A, and NONE 9A.

I highly doubt there is an error for your location (at least on a macroclimate or large-mesoclimate scale), salicaceae. As I tried to explain above, the way the data was interpreted (there's more info available about that online) may not fit the data YOU choose to use or the way YOU interpret the data, but that is not an indication that your methods are better or more accurate. A lot of checking, double checking, and triple checking has gone into this work. In the extremely unlikely event that there is a mistake for your area, you should send your proof in and let them take a look. The data collection on your part will not be easy. Many sources have been taken into consideration and significant amounts of calculation has been used to determine the best fit for a useful product for multiple uses.

BTW, from a "shoot from the hip" prospective, my area is rated too conservatively by the new map. Most local gardeners in my city consider themselves to be in the lower zone 8 range these days. The new map shows us in 7a.

While the map is an improvement from the old map, one still must use common sense and maybe a little bit of experience to determine what can be grown where.

If you don't like the tool, don't use it (IT'S NOT MANDATORY for the most part). Most of the rest of us will put it to work as best we can. Just as one can choose not to use the telephone or fly in planes, one can choose to ignore or even deny the usefulness of the new map.

Looking at my local map, elevation effects such as the valley I live in are often not well represented. But these are local effects. There is no data that takes in every square foot for every location. Much of it is extrapolated from various reporting stations, and these stations are usually many miles apart. Locally it is VERY difficult to forecast snowfall, as small difference in the atmosphere can have large consequences. One of the things I tell people about a weather forecast locally, is that the atmospheric sampling locations are usually 200+ miles apart. But from this data, and computer models that are relatively crude, plus some experience thrown in is what the forecasters have to estimate a 5 mile wide rain/snow line in forecasting snow/rain events days out, and sometimes the same day. A 1% difference in forecast relative humidity at any elevation can sometimes significantly move that line. Same with 1 degree, or any number of other factors.

FTR, I'm still borderline 6b in the new map, but we have broken into 6b easily the last couple years, and right at the border the other years I've lived here......except this year. 10 degrees on two occasions is the lowest it has been. This year borderline 7b/8a, last year -25 borderline 4a/4b. What a difference a year makes. Oh how I just want "normal" weather for a while. Not been allot of normal for several years.

Arktrees

I know most of you know this as well as I do, but for the sake of newbies who might not know...these hardiness zone ratings are based on the average of many years of data. Saying that the weather in a certain year represented a certain zone rating might mislead someone that didn't understand what you were getting at.

Perhaps I could google this and tool around but does anyone know off hand how many years they use for the average?

30. See the "About" tap.

Here is a link that might be useful: Link to

I wonder if the cold winters of the 70s had skewed the averages on the cold side before?

Good post.

I believe thirty is good for bushes and hostas. After cutting down suburban trees and counting rings it is my opinion a sixty year map would be appropriate.

Also good points about the microclimates. Gotta remember though, folks who browse tree forums are probably 1 of 1000 in their neighborhood. That makes us the top 1% far as caring to know about trees. The hardiness maps are simple enough anyone in town can look and decide.

Now if only the big box stores would get a copy....

wasnt there an article a while back.. about weather stations on top of blacktopped roofs .. next to air conditioner condensers... in the middle of parking lots.. enclosed in wooden fences.. etc ... the numbers are only as good as the source ...

my point wasnt really political.. nor global warming.. it has to do with verification of the raw numbers ....

it was more about questioning the sources of the numbers ... and not the guy who collated the numbers ...

just because the USDA publishes numbers.. does not mean to me.. that those numbers are true and proper ...

the whole point of the 60's was to question authority ...

and here we come now.. simply accepting un-verifiable numbers generated by a bureaucracy ... and i refuse such ...

my garden is not zone 6 .. and all the z6 plants that i tried pushing zone on died .. period .. so in my estimate .. the map is useless ... especially in regard to supporting any political theories ...

the number are unsupportable on my direct experience ... it simply does not matter to me what the USDA says ... my garden is NOT z6 ...

and we can not really debate micro climate with all this ... that always matters .. its just a digression to this discussion ...

so i guess my bottom line is .. prove to me the weather station provided verifiable numbers ... and to simply tell me.. big brother provided them.. doesnt really impress me ...

ken

Briefly, there have been studies that show the effects that many claim about heat island, roof top etc. simply are not valid. Those to make these claims in the media (not saying you Ken) are basically cherry picking data. Just as they are doing when there are headlines saying that scientist predict cooling for the next 30 years. The reality is that there are multi-decade occelations that influence the weather over North America and Europe, and these are due to switch to the phase that generally produce colder winter's for N. America and Europe than would be experienced otherwise in the warmer phase. The globe as a whole does not cool, it's simply a redistribution of heat. But the climate change opponents only include the typical cooling of NA and Europe.

Arktrees

Most of Ken's commments are money. Use the zone map as a baseline when you first start gardening.

Obersve your own micro-climates over the years and progress from there.

Always keep in mind you can never beat out the anomolies so plan accordingly.

Indeed. AGW is moving on up.

Amazing to witness this in a lifetime-- a boringly stable climate just turned up to 11.

The simple fact is that as others have pointed out, you plant for the odd smack in the face from mother earth or you push your luck based on the zones and what you can afford to lose.

I know I may get away with a fig tree in Z7 like others down in the valley do, but I also know that the in 4 short years I've lived here, my little micro climate up on the hill, with our tails facing north, has produced lows that would kill 'em back. So I don't grow 'em.

I don't question the data (especially after knowing a little about how it was collected) any more than I question whether I am really the only one on GardenWeb and all the other posts are just a mass conspiracy from "big brother" to spy on me. I do however question a little about how the data has been applied. There were many decision that had to be made regarding what data was used (how many years), how each year was weighted (I'm not sure what the decision was for the final product...I should try to check), and things like that. I also question the accuracy on a mesoclimate scale (not to mention the microclimates which I can understand would be hard to account for). When I look at Knoxville, for instance, there is nothing showing a difference between that area and the surrounding areas (even when I download the high-resolution version of the map). Like others have said, I think the map is a good baseline to start out with, but one must have experience or talk to others with experience in their area to really know what to expect. The climate is just to variable (from year to year, from place to place, etc) for one single no-questions-asked solution.

My zone went from borderline 5b/6a, to the middle of 6a. However, I will continue plant only fully zone 5 hardy plants in most of the gardens, because of the fact that my property is located on the outskirts of town, across from open farmland, and it gets blasted with bitter northwest winds (despite some windscreen).

The data is no doubt solid, but I wonder why a plant hardiness map would calculate the zones based on average lows. Plants that are truly hardy to a location have to periodically survive temps that are lower than just the average lows.

Not a problem. All you have to do is figure that a fully hardy plant needs to be at least 10 degrees hardier than the bottom figure of the average range given for the zone (that would work quite well in my area, anyway - some other places might get colder, I suppose).

Also, it's not necessarily about extreme cold events. It's not uncommon at all to find that plants can take much more cold, for a brief time, than what they are rated for. When a plant is given a hardiness zone rating, expected extremes are taken into account as much as possible. The decision about what temperature analysis (record extreme cold temperature, average minimum cold temperature, etc) to use has been considered and debated for a long time. The consensus so far has been to use the current hardiness zone ratings for that analysis. It's also not uncommon for better nurseries and horticultural authors to note further temperature, or even temperature linked with other climate conditions, parameters and experiences when discussing individual plants. Lastly, different plants respond quite differently to cold temperatures, so that further complicates using a single rating system.

Agree with brandon, they will surprise you that they in fact handle a few days of extreme cold. We have a Japanese Maple, and Chinese Pistache, and Oklahoma Redbud. All rated USDA 6b (0 to -5) or higher. We they all were hit with -25, -13, -8, -6, last winter. Not to mention many other very cold night, but not as cold as this. They ALL survived. No flowers on the redbud, and some small branch lose on the maple, but the pistache seemed almost unaffected.

Arktrees

This winter is unusually warm.

Ark, that is a pretty amazing. I really think its all that other hoopla that I mentioned above that effects the plant not just the temps.

Its been fairly cool here as well. I know that bitter old man will hit in Feb but so far, knock on wood, -3 was the low.

It could push zones down in 10-20 years.

Here is a link that might be useful: Forget global warming - it's Cycle 25 we need to worry about (and if NASA scientists are right the Thames will be freezing over again)

Lou,
I have seen that before. The amount of cooling is a small fraction of what is expected from CO2, and therefore of little consequence. The latest research indicates that the amount of UV radiation was significantly reduced, and that through some mechanism, this changed the jet stream so that Europe got colder. However the globe as a whole did not change much as indicated by multiple lines of evidence. Lastly, the claim of not warming for 15 years has now been debunked as well.

Arktrees

Oh boy, here we go again.....GardenWeb's gonna have to start a new forum: The Crackpot Conspiracy of the Day Forum.

...and I have just the guy picked out for moderator, or at least chief contributor.

If we were smart, we'd be 20 years into a massive CO2 reduction plan. It's way too late now. 350ppm isn't even a speed bump on the way to 450ppm+

Hello Eocene Epoch! I just wonder if it will last long enough for the old giants to spread?

Dawn Redwoods in the artic? Yes please.

Here is a link that might be useful: Flora of Eocene

This is the website related to the article that Ken mentioned...
http://gallery.surfacestations.org/main.php?g2_itemId=20

You can browse through photos of local long-term historical sites.

Here is a link that might be useful: Surface Stations gallery

No discussion of the temperature record is complete without debunkning the myth that the temperature record is unreliable or somehow skewed by heat islands.

http://skepticalscience.com/surface-temperature-measurements.htm

It's valid. The planet is warming. Man's activity is making a significant, measurable contribution to that warming. We (species) are set for "interesting times"

Here is a link that might be useful: http://skepticalscience.com/surface-temperature-measurements.htm

I've never found hellish widespread disruption and misery an interesting prospect.