http://anthropik.com/2007/01/usda-hardiness-zones-shifting-north/

Make sure you push the buttons.

The coldest temp at my home this year was -19. My zone was and is zone 5. Zone 5 means -10 - 20.

The zone map Janet linked to shows that I used to be the upper edge of zone 5 and now I am in the middle of it.

C'mon zone 6! I think climate change is a big deal, but at the same time I won't complain about warmer winters.

Depending on what map I look at, I've been zone 4 or 5 (right on the line, so it depends on how sharp the map is, how big, how thick the lines are, etc.).

I usually have plants that are for zone 4, but I have spots in the yard that are easily a 5, and I've even grown some for zone 6.

Personally, I think that the "new" zones are jumping the gun; the maps that I have seen thus far are unofficial. To my knowledge, the USDA still has not changed their models.

I remember growing up in Oshkosh with a next-door neighbor who had a peach tree. Wishful thinking, says I... but he got away with it for almost 10 years before a cold winter killed it. And that is the point... the hardiness zones are designed for long-term planning. For long-lived trees, vines and shrubs, they represent the safety margin that can avoid costly disappointments.

While the last decade has been warmer than the historical average, there is no reason to believe that such trends will continue unabated. It only takes one hard winter to destroy hundreds of dollars & years of patient care.

I might try pushing the zone for perennials that can be easily replaced; but for woody nursery stock, I will stick to the established zones.

I agree with zeedman. Milwaukee had -26F as recently as 1996 and though abnormal (tied a record), its enough to keep it zone 5a. I still have some zone 6 plants though. Just cant help pushing those zones ;-)

tj

The maps I've seen say Milwaukee is zone 5b. We're right near the lake and that helps keep us a little warmer than the counties west of us. I saw the Arbor map about a year ago (it was a larger version that showed the zones better). They had the areas in southern Wis. by the lake as zone 6. I've read they take 10 yrs and get the average lows. There's always expections, but on the average we've had warmer lows in the winter. It seems that when we do get those temps that are really low, we have a fair amount of snow to protect the plants.
I'm not going to take big chances on buying plants for a warmer zone, but I'm going to enjoy it if we don't get those super cold temps! LOL!!

Kat

Hi,
I have no doubt that global warming is real, but I'm not ready to adjust my zone yet. Also remember that ultamate temps are not the only factor. 2 other biggies are drainage and snow cover. I have found that there are quite a few things that I can grow here (Wausau area) that I could not grow in the Milw area and I think it has to do with having sand instead of clay and better snow cover. When it comes to woodies though I'm sticking with very hardy things. Looks like we'll have snow bunnies for Easter though. So much for global warming.

Zone maps do show Milwaukee as zone 5b, but that's a distortion because the weather service is at Mitchell Field. Those same maps show a zone 4b just about touching Milwaukee County's northwest corner. In my practical experience, 3-5 miles inland from Lake Michigan is really zone 5a.

tj

The way I look at the zone change,is to remember weather records have been kept just a little over 100 yrs - this earth has been turning for billions of yrs.If we are in a warming phase because of mans nasty habits or the last 100 yrs maybe were a little colder than average? If we had a couple thousand yrs on record,I would say thats more accurate. I still will try my luck with a few plants I really love.