Shifts in USDA plant hardiness zones

I came across this nifty map and want to share it with fellow permies showing some subtle shifts in the USDA plant hardiness zones as they creep northward with climate change. Click the three tabs at the top of the page to see the differences.

http://noaa.maps.arcgis.com/apps/MapSeries/index.html?appid=5f617f338eb5431eb3700e8685eccaf7

Sweet, 10 more years and I'll be in zone 5!!  

Mike Jay wrote:Sweet, 10 more years and I'll be in zone 5!!  

same here! thats great as a lot of great fruit that i couldn't grow before are now able to be grown here. as the last time the chart was made was 2010 which put me in z4 from 3, must be at least z4b by now as we're 8 ys later? if thats the case Mike, you are already z5.

I would love an international version. Or even just Canada.

-CK

Cool! Thanks for sharing! GIS story maps make it really easy to visualize this sort of data. No shift in zone for my property but not far from me along the coast some zone 9 spots showed up. I wonder if there are any micro-climate areas on my property that are already at zone 9...

Chris Kott wrote:I would love an international version. Or even just Canada.

-CK

it must be the same results for Canada. just figure at least 1 zone, nearly 2 warmer than you thought it was before you saw this map. maybe the Canadian growing zone map as already accounted for this change.

Daron Williams wrote:Cool! Thanks for sharing! GIS story maps make it really easy to visualize this sort of data. No shift in zone for my property but not far from me along the coast some zone 9 spots showed up. I wonder if there are any micro-climate areas on my property that are already at zone 9...

its possible. i have a few sheltered spots that are z5 . i know because i have a few bushes that are z5 and do fine there.

steve bossie wrote:

Chris Kott wrote:I would love an international version. Or even just Canada.

-CK

it must be the same results for Canada. just figure at least 1 zone, nearly 2 warmer than you thought it was before you saw this map. maybe the Canadian growing zone map as already accounted for this change.

Yeah, I think our zones shifted 2-3 years ago - I went from 2b to 3b. As far as I know though, we don't have any nice comparison maps like the one in the OP though. :(

One thing to remember is that the zones are arbitrarily selected by the Fahrenheit system (every 10 degrees F).  So when they came up with the system, the lines formed on the map and the zones were created.  Now that the climate is warming, those lines are sliding north.  So if you lived just north of the line, now you're south of it and you can say you're a zone warmer (yay?).  But in reality, it generally got warmer everywhere on the map.  So if you were zone 5a, now you may be 5b.  Also if you were at the north end of 6a now you may be at the south end of 6a.  Still the same zone but it's warmer.

I'm guessing that if you averaged it all out, the zone change is reflecting a 2-3 degree increase in the minimum winter temp.   So if you look at the right-most tab you may tend to think that if you're in a colored band you got a temperature raise and everyone else didn't.  But in reality everyone got warmer, the people in the bands just get to say they're farther up the scale.

TLDR:  I don't like the right chart because it could be construed to think that only some places get to garden more ambitiously.

Also bear in mind that in the lower zones, the amount of winter snowpack influences the actual zone a lot because it acts as an insulation barrier on top of the root system.

So for example let's say the average temperature in your area is warming, and it is resulting in a thinner snow pack. This might actually result in trees that were previously hardy dying from the winter cold.

Nick Kitchener wrote:Also bear in mind that in the lower zones, the amount of winter snowpack influences the actual zone a lot because it acts as an insulation barrier on top of the root system.

So for example let's say the average temperature in your area is warming, and it is resulting in a thinner snow pack. This might actually result in trees that were previously hardy dying from the winter cold.

with our 190 in.+ of snow this year even my sensitive plants will come out unscathed that is if the weight of the snow doesn't crush them.

The only problem with hardiness zones is they need to start taking into account the extremes we seem to be experiencing on a more regular basis.  

We have yet to experience in modern times the extremes of the cold snap of 1899 that brought -2 degrees F to Tallahassee, FL and Columbia, SC, an ice covered Mississippi at New Orleans, ice floes exiting the mouth of the Mississippi, and light frosts in Cuba.

This wiped out a lot of citrus in the traditional citrus growing regions of LA, MS, AL, GA, and northern FL and stimulated the USDA into starting research into cold hardy citrus which resulted in the numerous citrange, citrumelo, and other trifoliate hybrids that were developed in the early 1900's.

Mike Jay wrote:Sweet, 10 more years and I'll be in zone 5!!  

Yeah - me too, maybe....

Interesting.  Hope all the birds and insects/pollinators are getting copies so they can keep up.

It looks like we are in the northernmost zone 10 area in the U.S., wow! It has seemed like the climate here in the extreme NW of CA has followed central CA coast patterns more than temperate rainforest patterns for several long stretches over the time I've been living here. Hopefully the old growth patches of Redwood left here will be large enough to buffer catastrophic fire like they have for their entire multi-millenia existence. How do we convince people that the forest fire problems in CA are the result of not enough forests and not enough fire?

Much as I would like to believe it, I doubt the zones will simply shift predictably. My parents in WV have seen a warming of winters- but they still get late freezes anf snows. So their orchard blooms earlier thanks to the warm weather, then gets buried under a foot of snow.
We will have to see how things develop...

We had a warm February and a cold March and still cold into today, April 8. It's either been raining or snowing thru the whole planting season. I finally planted some radish and lettuce 3 days ago, 3 weeks late. The next day it snowed a couple inches. I guess I'm going to have to learn to plant in the snow. I'm thinking of going out with the seeds and a teaspoon. As I sow the seeds I can see the seeds so easy in the snow, when I have them too close together I can scoop them up with the spoon. Today the sun is trying to shine, but it's snowing also.

Have to learn to adapt.

Despite being moved up to zone 10, we had frosts and hail in March, 6weeks after our historic last frost date (January 17th normally). Perhaps counterintuitively, this seems to be in line with the likely results of climate change chaos rather than the woefully misleading term “global warming” that just let climate denialists make specious claims any time we get an odd snowstorm in April, even thought these are often caused by abnormally warm polar winters and subsequent high pressure forcing cold air to stay in temperate regions in abnormal patterns.