Goodbye Zone 5b. Hello Zone 6a. December 2023

My entire gardening life, I've been a Zone 5B gardener.  That means that my gardens have all lived in the USDA Zone 5b.  Just search for [Zone 5b] here on my blog and hundreds of posts will show up.  And, I suppose that I never considered that the maps change over time.  But..but...but...they DO!  They change.  In fact, they change every ten-or-so years and the USDA just (a couple of weeks ago) released their latest maps - the 2023 map.  The last time they released a map was 2012.  

What's different in this new map?  Well, for me:  A LOT.  I'm in a whole new zone.  So long, Zone 5b.  Hello Zone 6a.  

Dr. Trent Ford - The University of Illinois State Climatologist has a good explainer post up and talks about how the 5b/6a changes have taken place:
The boundary between zones 5b and 6a, representing an average annual extreme minimum temperature of -10°F, migrated 60 to 70 miles north, from around Springfield in the 2012 map to around Peoria in the 2023 map. The boundary between zones 6b and 7a, representing an average annual extreme minimum temperature of 0°F, migrated 40 to 50 miles north from Cairo in the 2012 map to the St. Louis Metro East area in the 2023 map. And for the first time we see a small sliver of zone 7b in the southern tip of Illinois. We also see an expansion of zone 6a around the broader Chicagoland area, spanning from Lake County to Kankakee County. The 6a expansion in northeast Illinois is likely due to a combination of long-term winter warming and urban sprawl and development in the region.
(emphasis, mine.)

I'm in that '6a expansion'.  But...JUST BARELY.

You can put your zip code into the USDA map and see where you land.     We live inside this circle.  You can see that while we're now in the green (6a), the border for 5b is like...a couple of blocks away.  


What does the zone change mean?  I'm not sure.  Are we *really* 6a?  Or, if they move the border of the zones up a couple of blocks, might we still be in the same zone as we've always been?  

I've looked around to see if there are lists of "plants to work in Zone 6a, but aren't hardy to Zone 5b?" and I haven't found anything.  But, I'm guessing some of the nurseries around here might start to introduce some new plants in the Spring.  For me, the thing that I'm (mostly) thinking about are Zone 6 Japanese Maples - there are tons of them.  Might we be able to host a Zone 6 JM?  

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