General 2023 USDA Plant Hardiness Zone Map Discussion

[Hardypalms]

On 11/17/2023 at 11:49 AM, JJPalmer said:

Jumping off the FL-specific thread, I figured I'd start a general discussion on the release of the latest map by the USDA: https://planthardiness.ars.usda.gov/

Kicking things off, a few interesting things I've found:

• Inclusion of a significant amount of 10a throughout SE Louisiana including a small section in DT New Orleans along with a *very* small amount of 10b
• Northernmost extent of 10a extends into SW Oregon (Brookings)
• Poor representation of cold sinks in microclimates throughout the Rockies: Jefferson, CO hit -24f a couple of weeks ago during a fairly typical October cold snap, but they're listed at 5a (-20f to -15f) and will routinely fall below -25f.  Peter Sinks in Utah hit -60f last year and hits -40f several times annually and is listed as 4a
• 10b in S Texas (makes sense) despite significant freeze a couple of years ago
• General trend of warmth nationwide (ex. introduction of zone 6 in Wisconsin for the first time, reduction of zone 4 throughout the nation)
• Better ability to handle UHI than prior (ex. Minneapolis and Orlando)

Wow I m in 8a now. Holly mackerel!!!

No wonder i keep Sabal palmetto, Butia capitata, Sereona repens with some protection.

 

Thxs for this thread.

Pat

[SeanK]

Taking another look, I notice z8b in NE GA. An area between Hartwell, Toccoa, and Seneca, SC is rated z8b. Not sure what the minimum temps were in December, 2022.

[KsLouisiana]

On 11/18/2023 at 4:12 AM, RFun said:

It's perfectly legit to me.  Water plays a big role in that.  There's a larger area of 10b than that, but there aren't many weather stations in that unpopulated area.

Have y'all been to the stretch of Louisiana from Belle Chase to Venice? It's surrounded by water like you said.  By the time these big cold outbreaks hit there from  the west they are totally weakened. Also they commercially grow citrus and they have the biggest Majesty palms I personally have ever seen.  It's quite  Palmyra down there lol

[SeanK]

Always interesting to look across a series of these maps and notice trends and cycles.

 

[SeanK]

Just be careful in how the zones are defined.

[Aceraceae]

What year is the more detailed first one? 

The second one is very wonky and has colors out of order, just like the 1990 map printed in the Rodale Organic Gardening questions and answers hardcover book from about 2000. 

Where is the "reverse side for instructions on how to use this map" or at least the data set used? 

[flplantguy]

The older map from 1948 was not a standard or researched i dont think, but the top one from the early 60s (IIRC) is from the USDA. Likely had no political bent and was researched more. I like to compare it to the newer ones to see where things have actually changed.

[kinzyjr]

8 hours ago, flplantguy said:

The older map from 1948 was not a standard or researched i dont think, but the top one from the early 60s (IIRC) is from the USDA. Likely had no political bent and was researched more. I like to compare it to the newer ones to see where things have actually changed.

There was an article in the last published CFPACS quarterly, The Palmateer, that discussed a few of the various zone maps released over the years.  The article starts on page 4 of the attachment.  The Zone Maps included:

• a 1936 map based on data from 1895-1935
• the 1960 map (closer to the 2012 map)
• the 1990 map
• the 2012 map
• the 2023 map

Without being sure how much longer it will take to get our site completely migrated and updated, I'm not sure if/when another publication will be available, so might as well share while it's available.

20240101_Palmateer_Holiday_2023.pdf

[flplantguy]

So then that is a color version of the 1960 map.  That makes sense because that means it was released before the 62 freeze (and the other freezes in other areas of the world that year and 63) that ushered in the dark ages of tropical plant growing here.  May they never again come to pass🤞.

[SeanK]

On 7/16/2024 at 7:20 PM, flplantguy said:

So then that is a color version of the 1960 map.  That makes sense because that means it was released before the 62 freeze (and the other freezes in other areas of the world that year and 63) that ushered in the dark ages of tropical plant growing here.  May they never again come to pass🤞.

The 1970s were dark times as well. 1985, the bottom fell out.

[wannabepalm]

I'll be visiting Hilton Head, SC in mid October this fall. Listed as 9b on the 2023 map. Georgia shows nothing higher than 9a. Should be interesting - I'll report back with some palm photos!

[SeanK]

On 8/26/2024 at 3:26 PM, wannabepalm said:

I'll be visiting Hilton Head, SC in mid October this fall. Listed as 9b on the 2023 map. Georgia shows nothing higher than 9a. Should be interesting - I'll report back with some palm photos!

Take a walk around Bluffton and note the difference in palms as you head eastward. Mainland plantings more z8b. Butia, Sabal, Chamaerhops. Farther east, Washies and Phoenix. I haven't been in a long time. I don't recall Queen palms.

Hibiscus rosa-sinesis as a dieback perennial 

[wannabepalm]

52 minutes ago, SeanK said:

Take a walk around Bluffton and note the difference in palms as you head eastward. Mainland plantings more z8b. Butia, Sabal, Chamaerhops. Farther east, Washies and Phoenix. I haven't been in a long time. I don't recall Queen palms.

Hibiscus rosa-sinesis as a dieback perennial 

I’ll do it!