2023 USDA Plant Hardiness Zone Maps Out

[MarcusH]

1 hour ago, Allen said:

From the USDA Page https://planthardiness.ars.usda.gov/pages/how-to-use-the-maps

"

If your hardiness zone has changed in this edition of the USDA Plant Hardiness Zone Map (PHZM), it does not mean you should start removing plants from your garden or change what you are growing. What has thrived in your yard will most likely continue to thrive.

Hardiness zones in this map are based on the average annual extreme minimum temperature during a 30-year period in the past, not the lowest temperature that has ever occurred in the past or might occur in the future. Gardeners should keep that in mind when selecting plants, especially if they choose to "push" their hardiness zone by growing plants not rated for their zone. In addition, although this edition of the USDA PHZM is drawn in the most detailed scale (1/2 mile square) to date, there could still be microclimates that are too small to show up on the map.

Microclimates, which are fine-scale climate variations, can be small heat islands—such as those caused by blacktop and concrete—or cool spots (frost pockets) caused by small hills and valleys. Individual gardens also may have very localized microclimates. Your entire yard could be somewhat warmer or cooler than the surrounding area because it is sheltered or exposed. You also could have pockets within your garden that are warmer or cooler than the general zone for your area or for the rest of your yard, such as a sheltered area in front of a south-facing wall or a low spot where cold air pools first. No hardiness zone map can take the place of the detailed knowledge that gardeners learn about their own gardens through hands-on experience.

Many species of perennial plants gradually acquire cold hardiness in the fall when they experience shorter days and cooler temperatures. This hardiness is normally lost gradually in late winter as temperatures warm and days become longer. A bout of extremely cold weather early in the fall might injure plants even though the temperatures may not reach the average lowest temperature for your zone. Similarly, exceptionally warm weather in midwinter followed by a sharp change to seasonably cold weather may cause injury to plants as well. Such factors could not be taken into account in the USDA PHZM.

All PHZMs should serve as general guides. They are based on the average lowest temperatures, not the lowest ever. Growing plants at the extreme range of the coldest zone where they are adapted means that they could experience a year with a rare, extreme cold snap that lasts just a day or two, and plants that have thrived happily for several years could be lost. Gardeners need to keep that in mind and understand that past weather records cannot provide a guaranteed forecast for future variation in weather.

Other Factors Affecting Plant Survival

Many other environmental factors, in addition to hardiness zones, contribute to the success or failure of plants. Wind, soil type, soil moisture, humidity, pollution, snow, and winter sunshine can greatly affect the survival of plants. The way plants are placed in the landscape, how they are planted, and their size and health might also influence their survival.

•    Light: To thrive, plants need to be planted where they will receive the proper amount of light. For example, plants that require partial shade that are at the limits of hardiness in your area might be injured by too much sun during the winter because it might cause rapid changes in the plant’s internal temperature.

•    Soil moisture: Plants have different requirements for soil moisture, and this might vary seasonally. Plants that might otherwise be hardy in your zone might be injured if soil moisture is too dry in late autumn and they enter dormancy while suffering moisture stress.

•    Temperature: Plants grow best within a range of optimal temperatures, both cold and hot. That range may be wide for some varieties and species but narrow for others.

•    Duration of exposure to cold: Many plants that can survive a short period of exposure to cold may not tolerate longer periods of cold weather.

•    Humidity: High relative humidity limits cold damage by reducing moisture loss from leaves, branches, and buds. Cold injury can be more severe if the humidity is low, especially for evergreens."

That's what I basically mean because people get all excited now start planting palms in Chicago without protection 😄.  The average temperatures went up and winters get milder , less cold fronds but the polar vortex outbreaks could happen more often but that's not scientifically confirmed YET. So long story short nothing has changed for gardeners.  

[Las Palmas Norte]

Meanwhile, all along the Pacific Coast ... unaffected and stable.

[ZPalms]

9 hours ago, DAVEinMB said:

If your zone has gone up it just means that historical temperature data shows a warming trend over the observed time frame.

Now that you're designated 8b will you never see an 8a winter, no. Will they be fewer and farther between, yes. 

 

I suppose it makes sense why we don't see snow like we used to here. Also, it sort of makes sense why Chamaerops and cycads can thrive here. A decade ago, that wouldn't have been the case, at least for Chamaerops. I know cycads have been successful for years. Would it still be too early to consider myself 8b and update that on my profile 😂?

Edited November 16, 2023 by ZPalms

[Dartolution]

This has certainly been an interesting release. 

There appears to be a near 200mile shift in Alabama. Zone 8b previously began around the Alabama-Florida line - and now extends all the way up to near Birmingham. 

I was about 30miles into zone 8a, and now am roughly 10 miles into 8b. 

Thats a fairly significant temperature shift over the last 30 yrs. 

While it really doesn't change anything in the garden - it is pretty shocking to me. 

Is it too early to change my zone rating on my profile? 

[DAVEinMB]

49 minutes ago, ZPalms said:

Would it still be too early to consider myself 8b and update that on my profile 😂?

Not as far as the USDA is concerned 😄

Edited November 16, 2023 by DAVEinMB

[Dartolution]

Evidently not. 

It does appear that the biggest change occurred in the deep south. 

Possibly from the warming gulf buffer. 

[Silas_Sancona]

1 hour ago, Las Palmas Norte said:

Meanwhile, all along the Pacific Coast ... unaffected and stable.

...Not  ..completely.  Though the changes are more subtle....  

More 11 along portions of Los Angeles county beaches / Coastal Ventura Co., near downtown San Diego ( though they could easily extend 11 along the entire coast of S.D. County, to about Oceanside ..maybe further north.. / expand it east of Downtown / south to the border.  ..and a few specks of 11 right along the coast between San Luis Obispo and Big Sur..

 10 for Santa Cruz proper / more coverage of z10 in / around Monterey

More solid 9b ..and some 10A in the Inland Empire.. 10B in some areas near Palm Springs.. ( Next update = Guarantee 10 will fill in the currently 9b gap between Corona?? ...and the Palm Springs side of the Banning Pass )

There is also a little 10 right on the coast on either side of the CA. / Ore. border ( Del Norte / Josephine ) ..also see some extra bits of 9B along the coast in Washington..

..So, yea.. lol.. Might be quite subtle, compared to many areas back east at least  -for now anyway-  but things are a changin',  ..even on the " Best Coast "

[Xenon]

Zone 10A creeps into the Houston Area covering all of Galveston Island, most of the Bolivar Peninsula, and along the Bay from Texas City to San Leon

 

 

Zone 10B officially "exists" in the state of Texas in Port Isabel/South Padre and also SpaceX (Elon needs to hurry up and make Starbase a tropical paradise)

 

 

Think my crude map from January 2021 did quite well 😆

 

Edited November 16, 2023 by Xenon

[DTS]

Zone 6 is now touching the U.P. I noticed that 2 islands that have zone 7a on them northwest from Traverse City, but it doesn't say on the downloadable maps for Michigan that it's there

[RFun]

5 hours ago, DTS1 said:

Zone 6 is now touching the U.P. I noticed that 2 islands that have zone 7a on them northwest from Traverse City, but it doesn't say on the downloadable maps for Michigan that it's there

Yeah, that would be the cold version of 7a.  Certainly different from the 7a found much further south.

[SeanK]

On 11/15/2023 at 9:06 AM, ChicagoPalma said:

Yay, while im rated zone 6a/6b, but my winters say the other! But that means technically Im in the region where palms can grow! Needles and sabal minors unprotected.

I'd still be careful. 

z7a from I94 to Lakeshore Dr but the ground is a huge heat sink to the west. That frozen ground is tough on herbaceous roots. A random night at -2°F versus an entire z6b is a big difference, too.

 

[SeanK]

My area moved from a marginal 10°F to about 13.5°F. This is realistic for a 9-year average. It's year #10 like we had last year at 5° F that's the problem.

[AcerPALMatum]

Panhandle florida is now showing pockets of 9b in coastal areas of Destin and Pensacola. I'll use this as license to try my luck with Queen palms, especially given there are some 10-15' tall ones in the neighborhoods around me. I am surprised how much the 9a boundary shifted inland.

[MarcusH]

24 minutes ago, AcerPALMatum said:

Panhandle florida is now showing pockets of 9b in coastal areas of Destin and Pensacola. I'll use this as license to try my luck with Queen palms, especially given there are some 10-15' tall ones in the neighborhoods around me. I am surprised how much the 9a boundary shifted inland.

Check your record lows for the last 3 to 5 decades . If it gets below 20°F don't even bother planting Queens unless you don't mind worrying about it every winter.  The new map doesn't change anything it just makes people here think they can try new palms. 

[AcerPALMatum]

38 minutes ago, MarcusH said:

Check your record lows for the last 3 to 5 decades . If it gets below 20°F don't even bother planting Queens unless you don't mind worrying about it every winter.  The new map doesn't change anything it just makes people here think they can try new palms. 

They're cheap enough I'm not stressed to be honest. Lol. They're definitely living on borrowed time here. Plenty survived 18-19 degrees this past winter, but I'm sure something sooner or later will kill them.

[WSimpson]

I'm 8A  for the first time , which is correct for my average lowest Lows , which is a 30 year average Low of 11 point something Fahrenheit , but I have 7B winters 3-4 winters out of 10 winters . 

Still it's cool to be 8A . Damn , I can't brag about my palms being in 7B anymore  lol !

Will

 

 

 

I'm 8A by 300 yards . Awesome ! 

 

Edited November 17, 2023 by Will Simpson

[palmtreeguy]

On 11/15/2023 at 2:48 PM, fr8train said:

Does anyone know how they get the information in order to determine where the actual line between zones is, like below? 

They use data from the PRISM Climate Group which factors in elevation, then weather station data etc. is added in.  All of this is data is fed into computer programs that extrapolate areas between stations.  Elevation such as hill and mountains are big factors in temperature of course.  You can see on that map those warmer areas are river valleys. 

[palmtreeguy]

On the map I went from 7b to 8a (First thing in my mind: Sabal palmetto recommended hardiness zone lol).  I never thought that would happen, it's always been 7a/7b in my mind for well over a decade. 

I did some calculation here based on real weather station data and the map is correct for 1991-2020 I calculated and average of 10.14 F. 

But when I factored in more recent winters 1994-2023 I got an average of 9.55 F.  So I plan to stick with 7b for now  LoL

 

BTW Coconut palms can now grow at the very tip of LA at the Mississippi river delta zone 10b lol:

 

 

Edited November 17, 2023 by palmtreeguy

[jwitt]

@palmtreeguyBTW Coconut palms can now grow at the very tip of LA at the Mississippi river delta zone 10b lol:

No, that actually was three years ago.

[palmtreeguy]

9 minutes ago, jwitt said:

@palmtreeguyBTW Coconut palms can now grow at the very tip of LA at the Mississippi river delta zone 10b lol:

No, that actually was three years ago.

Yeah Sort of,  it's the 2023 issued map but based on 1991-2020 temps.   Based on warm cycle patterns in the eastern U.S.  that I've researched, it looks like we are heading back into a warm period for at least the next 5 to 15 years or so.   In 5 years the very southern tip of Louisiana will likely be a full on 10b and not just one pixel like that.

[RFun]

12 hours ago, SeanK said:

I'd still be careful. 

z7a from I94 to Lakeshore Dr but the ground is a huge heat sink to the west. That frozen ground is tough on herbaceous roots. A random night at -2°F versus an entire z6b is a big difference, too.

 

Those are some harsh conditions there with wind and ice to consider.  Other factors for plants would be the snow protection that is more reliable in areas of Upstate New York and Northern Minnesota.  Regarding palms, growing will be difficult, at best.  Downtown Chicago would be the better area, but there isn't much space lol.

Edited November 17, 2023 by RFun

[RFun]

7 hours ago, palmtreeguy said:

On the map I went from 7b to 8a (First thing in my mind: Sabal palmetto recommended hardiness zone lol).  I never thought that would happen, it's always been 7a/7b in my mind for well over a decade. 

I did some calculation here based on real weather station data and the map is correct for 1991-2020 I calculated and average of 10.14 F. 

But when I factored in more recent winters 1994-2023 I got an average of 9.55 F.  So I plan to stick with 7b for now  LoL

 

BTW Coconut palms can now grow at the very tip of LA at the Mississippi river delta zone 10b lol:

 

 

From what I've seen, Sabal Palmettos tend to do quite well in many areas of strong 7b and up.  Sabal Mocksville variety is probably the best for strong areas of 7b and weaker areas of 8a.  Anyway, just a guess. 

Edited November 17, 2023 by RFun

[RFun]

11 hours ago, AcerPALMatum said:

Panhandle florida is now showing pockets of 9b in coastal areas of Destin and Pensacola. I'll use this as license to try my luck with Queen palms, especially given there are some 10-15' tall ones in the neighborhoods around me. I am surprised how much the 9a boundary shifted inland.

Rightfully so.  If anything, these maps are still understating the warming effect of the ocean.  Far Northeast Florida does look to have quite a contrast from the water to the Alabama border area.  But, again, those cold snaps are short.  So only the sensitive vegetation is really going to notice the difference very much.

Edited November 17, 2023 by RFun

[teddytn]

I know people dislike when this is said….There is a huge difference between a northern zone 7 vs. a southern zone 7. In Tennessee for example the ground doesn’t freeze, and we don’t have sustained below freezing temps. Farther north in the eastern half of the U.S. near the ocean or a large body of water, absolutely the low temps for a given year or period of years may designate the area as zone 7 or whatever. BUT if the ground freezes solid, and the area has sustained below freezing temps for weeks or months on end, which is super common in the Northeast, even though the low temps still qualify it as zone whatever, do not expect your palms to survive unprotected. Just because in the past a Sabal minor or Needle palm survived seriously low negative temps for a short duration, does not equal them being designed to handle prolonged winter weather. Sorry these are just facts. Please plant whatever you want, wherever you want, just be realistic about having to protect your plants according to your location and not what your areas zone designation is. 

[SeanK]

43 minutes ago, teddytn said:

I know people dislike when this is said….There is a huge difference between a northern zone 7 vs. a southern zone 7. In Tennessee for example the ground doesn’t freeze, and we don’t have sustained below freezing temps. Farther north in the eastern half of the U.S. near the ocean or a large body of water, absolutely the low temps for a given year or period of years may designate the area as zone 7 or whatever. BUT if the ground freezes solid, and the area has sustained below freezing temps for weeks or months on end, which is super common in the Northeast, even though the low temps still qualify it as zone whatever, do not expect your palms to survive unprotected. Just because in the past a Sabal minor or Needle palm survived seriously low negative temps for a short duration, does not equal them being designed to handle prolonged winter weather. Sorry these are just facts. Please plant whatever you want, wherever you want, just be realistic about having to protect your plants according to your location and not what your areas zone designation is. 

Agreed. One night at -2°F every 20 years is different than z6b. No palm originates from an area where the ground freezes solid. Herbaceous roots cannot tolerate it.

[RFun]

1 hour ago, teddytn said:

I know people dislike when this is said….There is a huge difference between a northern zone 7 vs. a southern zone 7. In Tennessee for example the ground doesn’t freeze, and we don’t have sustained below freezing temps. Farther north in the eastern half of the U.S. near the ocean or a large body of water, absolutely the low temps for a given year or period of years may designate the area as zone 7 or whatever. BUT if the ground freezes solid, and the area has sustained below freezing temps for weeks or months on end, which is super common in the Northeast, even though the low temps still qualify it as zone whatever, do not expect your palms to survive unprotected. Just because in the past a Sabal minor or Needle palm survived seriously low negative temps for a short duration, does not equal them being designed to handle prolonged winter weather. Sorry these are just facts. Please plant whatever you want, wherever you want, just be realistic about having to protect your plants according to your location and not what your areas zone designation is. 

I agree.  The 6b that the map shows in the Chicago area around the lake is much different than 6b areas of say, Southern Missouri, where you see Magnolias.

[ChicagoPalma]

1 hour ago, RFun said:

I agree.  The 6b that the map shows in the Chicago area around the lake is much different than 6b areas of say, Southern Missouri, where you see Magnolias.

I used to have a southern magnolia, but it was in a small area and protected and sheltered up front the house, it bloomed very nicely.

[Southwesternsol]

My exact location didn't change, and I would argue it's still a little off in various locations in the west. Naturally when you have a lot of elevation and weather stations and populations are spread thin, it's hard to get perfect results. However, I do see a general improvement in the four corners region in regards to data resolution. I'm seeing some mountains and canyons and valleys that weren't present before hand.

Interestingly, looking through the region I noticed some 7b in Colorado, not in Montezuma county (although I wouldn't be suprised if there actually was and the data is just lacking) but in the mountains of La Plata county. I'm assuming it's most likely just odd or incorrect data, but maybe there is a little 7b microclimate in the foot hills surrounding Durango.

[WSimpson]

I just checked eastern NC and there is a pretty large area of 9A now .  Cedar Island is 9A , so it is inland  of the Outer Banks with less wind and probably better soil . I would think that area of NC 9A would be the place to experiment with less hardy palms .

I don't think much of the outer banks has had a frost yet , but that inland 9A area may have had a frost  . When the  next major cold snap  comes down I'll check for frost or freeze warnings there . 

Will

 

[RFun]

17 hours ago, ChicagoPalma said:

I used to have a southern magnolia, but it was in a small area and protected and sheltered up front the house, it bloomed very nicely.

I'm sure the Magnolias can take some cold, but the Chicago area is pretty harsh.  Protection would be a must for me.

Edited November 18, 2023 by RFun

[RFun]

14 hours ago, Will Simpson said:

I just checked eastern NC and there is a pretty large area of 9A now .  Cedar Island is 9A , so it is inland  of the Outer Banks with less wind and probably better soil . I would think that area of NC 9A would be the place to experiment with less hardy palms .

I don't think much of the outer banks has had a frost yet , but that inland 9A area may have had a frost  . When the  next major cold snap  comes down I'll check for frost or freeze warnings there . 

Will

 

I'd definitely be experimenting with various varieties there.  That isn't a bad area for quite a few cold hardy palms that aren't considered to be at the top of the cold hardy list.

Edited November 18, 2023 by RFun

[Swolte]

College Station TX now being 9a, however, I note that only winters up to 2020 were taken into account.  The subsequent winters (either in absolute lows or early polar vortexes) were devastating to 8b-listed plants and obliterated any 9a plants.

Moving forward, for the vast majority of plants I'll be spending money on, I will be aiming for z8a or lower.

Sabal paradise!

[Las Palmas Norte]

4 hours ago, Swolte said:

... Moving forward, for the vast majority of plants I'll be spending money on, I will be aiming for z8a or lower.

Sabal paradise!

I'm also an advocate of creating a strong foundation of proven palms, then expanding with some experiments, knowing full well that the possibility they may succumb at some future date.

[Turtlesteve]

So I'm rated as zone 8B now, but I just got to 12F last winter.  And we now have zone 9B on the SC barrier islands?  Yeah... good luck growing those 9B palms guys.  Might get a few years out of them.  The USDA zone maps are really of limited utility here, being in a continental climate where the annual minimum varies so much year to year.

What would be far more useful is to have maps based on probability - e.g. what annual minimum temperature do I have a 95% chance of staying above?  I assume this data is available somewhere and it would be possible to make such maps.

[Allen]

2 minutes ago, Turtlesteve said:

So I'm rated as zone 8B now, but I just got to 12F last winter.  And we now have zone 9B on the SC barrier islands?  Yeah... good luck growing those 9B palms guys.  Might get a few years out of them.  The USDA zone maps are really of limited utility here, being in a continental climate where the annual minimum varies so much year to year.

What would be far more useful is to have maps based on probability - e.g. what annual minimum temperature do I have a 95% chance of staying above?  I assume this data is available somewhere and it would be possible to make such maps.

You can do that in a few minutes on a spreadsheet if you have NOAA data available

[South Carolina palms]

9A finally encompasses much of Charleston metro which is exciting for me because now I can finally say I’m 9A. 

[Allen]

18 minutes ago, Turtlesteve said:

What would be far more useful is to have maps based on probability - e.g. what annual minimum temperature do I have a 95% chance of staying above?  I assume this data is available somewhere and it would be possible to make such maps.

Charleston, SC 95% above 11F based on data from 1950-2023

[LeonardHolmes]

Williamsburg VA moved to 8a and Kill Devil Hills/Colington NC moved from 8b to 9a.  In both cases still very close to the old zones.  It seems realistic and I have new optimism for a mule palm and a Jubaea I planted at the beach.  Now we just need some rain...

[MAPalms]

My little corner of MA has gone up quite a bit. Interesting to see 7b on Cape Cod….. wasn’t expecting that. I guess it could make sense for Nantucket though. I’m still technically 6b, but 7a is 5 miles from me. 35 miles from 7b.

[Nomad NYC]

Oh goody...According to the new USDA map, my part of NYC has changed from 7B to.....7B.