New USDA plant hardiness zone map

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Washington Post.

This has been a big problem for the USDA. A few years ago, they contracted the American Horticultural Society to revise the plant hardiness map, and the results displeased a lot of users who thought that nudging the zones northward wasn't justified. The new map was done by Oregon State University, which has done a huge amount of work on mapping American climate. USDA.

USDA eagerly points out that the map isn't intended to validate climate change. There's just vastly more data available than when the previous map was released in 1990.

My place seems to have just barely sneaked into zone 10A. And St Petersburg, too??

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There's certainly been a change in the old home state of Ohio.

The state is now almost entirely Zone 6, with a few little patches of Zone 5.

Before, there was a large, solid band of Zone 5 that ran from about 30 miles south of Lake Erie to about 10 miles south of Columbus.

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Thinking about it some more, that Ohio map also highlights the problem with the USDA system, which only deals with averages.

The Cleveland area is in Zone 6b, which, according to the map doesn't get any colder than -5 F, right?

Oh, I wish, but wrong. That shows the extreme lows in any given year, averaged for all of the years from 1976 to 2005. In other words what that map shows is that the average extreme winter lows for all the years 1976 to 2005 was between -5 and 0 F. The occasional way-low extreme extreme gets buried in the overall average.

Oh, how well I [expletive ] know! Guys and gals, I know for a [expletive] fact that it got a lot colder than -5 FF, in Cleveland. In 1977, 1978, and 1985 we were treated to temps well down into the mid-20's FF BELOW ZERO WITHOUT WIND CHILL in the Cleveland area. Red Converse All-Stars only emerge in the spring . . . BRRRR

California here I stay, ain't going back east, nuh-uh, no way . . .

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You think extremes are bad in Ohio? Florida, too, has direct access to Siberia. My purportedly 10A yard has to be planned for 23 degrees, and for 30 nearly every winter. St Petersburg is really blessed by its peninsular position. Orlando may be a bit better off than the map shows, due to urban heat island effects. Leu Gardens' position on the south side of a smallish lake certainly helps, a little bit.

I remember a staffer at the Washington Park Arboretum in Seattle (zone 8b?) marveling that their Florida torreya tree had survived a terrible cold spell, maybe 7ยบ F. I had to tell them that the native populations west of Tallahassee (8b) had gone well below zero (and so had the Rhapidophyllum palms on the same river bluffs). I'm wobbly about those hardiness zones--but it seems about right that Seattle and Tally would be in the same one.

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Dave and Dave,

The map is better, but not that much better, they'll never get Washington right! To many other factors to consider.

What I don't like for WA is the map is so small you can't even see where the 9a are, and the 8b-9a colors shades are to close of the same color to tell in WA.

Five miles south of me is 7b, they change it to the same as me 8a. It was just three years ago they had a low in that area of -02F (olympia airport), while I had 10F-12F in town... but yet were both 8a!

Also because Olympia is so close to that cold pocket, we can have an 8a winter followed by 9b winter. So what is my Zone?

Dave believe it or not there are some place in Seattle that have never been below 17F in 15-20 years, and the Washington Park Arboretum is 8b it not the warmest spot being on a hill.

Just my two cents.

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Edited by Palm crazy
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I think in general the map is too conservative, I.e. at least for FL. I know SW Dade county has more winters with mins in the 30s than not, yet it's called 11a.

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Looks good for my area, which is Pasco county just north of Tampa. Even if you include 1989 and its 23F two nights lows, 27F was hit in 1996 and 27-28F the past two winters here at my New Port Richey coastal home. I believe in 2003 there was a quick 28F low but that is the lowest I can remember, and my memory on cold snaps is pretty good. 9b is what i consider myself but on a good winter that does not always happen. Greg

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Here's the SoCal map. I blew it up so you could zoom in a bit. Pretty useless for CA if you ask me.

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If you go to the / Interactive Map / you can zoom in to see your area and garden zone up close, now I can see the z9a in WA. :D :D :D

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I like the map much better than the old one. At least now they recognize the fact that not everything is equally tropical once you get into zone 11 and there is a need for zones 11-13 with a/b breakdowns.

Florida seems to be pretty accurate, except I thought that there would be a heat island or two in the Orlando area that would qualify as 10a.

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I think in general the map is too conservative, I.e. at least for FL. I know SW Dade county has more winters with mins in the 30s than not, yet it's called 11a.

John, MIA airport average annual extreme minimum temperature for the map period of 1975-2005 is 39.23F or just inside 10b. Many places in Dade Co. have milder winters than the airport, so they ought to be 40F+ and qualify as 11a.

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I think in general the map is too conservative, I.e. at least for FL. I know SW Dade county has more winters with mins in the 30s than not, yet it's called 11a.

Displaced Floridian, I am pretty sure the color on the map that you are thinking is 11a is actually 10b, in which case the shading of the southeast tip of Florida is pretty accurate.

Also, I think they could have added a circle of 10a for the Orlando urban area. Finally, the 10a should run a tad higher on the east coast (right on the coast). Merritt Island is definitely zone 10a.

-Michael

Edited by palmsOrl
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I like the map much better than the old one. At least now they recognize the fact that not everything is equally tropical once you get into zone 11 and there is a need for zones 11-13 with a/b breakdowns.

Florida seems to be pretty accurate, except I thought that there would be a heat island or two in the Orlando area that would qualify as 10a.

OK I'm going to cry foul now. When I search for my zip code I get 10a, which is correct for most of Northern Sarasota County west of I-75. Then I put the zip for the SRQ airport and I get 9b. I have all the numbers for SRQ 1975-2005 and the average is 30.8F, clearly 10a. It's OK to estimate an area wrong, but they have to at least get the airports right. That's where they have the most accurate stations.

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Tampa's Interbay Peninsula is zone 10A on the new map. They have most of Pinellas in zone 10 which is overdone.

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10a in metro Orlando would only show up on the blow up interactive map but definitely pockest near downtown, around the lakes in Winter Park and Windemere.

9b is generous NW of Orlando. There are lots of cold pockets out past Apopka that are 9a maybe borderline 8b.

And I agree 10a should extend up to Cape Canaveral, maybe even extreme southern Volusia County and 9b should go to coastal areas up to Jacksonville.

Other than that it looks accurate

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And why not use 50 years or more of data ? I think that would indicate a better average.

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And why not use 50 years or more of data ? I think that would indicate a better average.

Eric, there are a couple of reasons they went with 30. The first one is that 30 years is a WMO recommended period for all weather averages, because of the climate fluctuations. The second reason is that the number of weather stations in the US tripled in the 70s. The biggest problem with the 1990 map was that they actually went with the 12 year period. The intent was to go with a 30 year period (1956-1986) just like they did in the 1960s, but that would only give them around (I could be off I only vaguely remember the ballpark) 2,500 stations with 30 years worth of data nationwide to work with. So they went with the 1974-1986 12 year period, which allowed them to use data from over 7,000 stations. This made the map more geographically accurate, but off by half-a-zone or so, because that happened to be one of the coldest 12 year stretches in the US history.

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The thing to remember is nothing has really changed. Like before, this doesn't guarantee that another catastrophic freeze can't present itself and set all of our gardens back a zone. Years of growth can still be destroyed in a matter of hours. Whether you have 25 degrees every year or once in ten years, you still can't grow things reliably long term. A better reference is still to look around and see what has grown well and survived the countless winter seasons.

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Zone 9b has gone from the southernmost counties in Texas in the 1990 map to near the Louisiana border in this map, a 300 mile difference!biggrin.gif 10a goes all the way up to Port Aransas near Corpus Christi...

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:) Jonathan

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Well I previously lived in a 9a area, haven't moved and now apparently live in a 9b zone. I personally think we are still 9a, global warming or not. Seems like we have had more frost/ice to scrape off of our car windows over the last few years and it sure feels more like Chicago to me! Can't wait to set up a better temp monitoring system than we have to track it ourselves.

Personally I would love to add a Howea belmoreana (sentry palm) but think a Livistona muelleri (dwarf fan palm) would be a better bet. I still think the Sunset zone for our area is more accurate.

Edited by WestCoastGal
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Tampa's Interbay Peninsula is zone 10A on the new map. They have most of Pinellas in zone 10 which is overdone.

I don't know, I think central and southern Pinellas as a zone 10a is pretty accurate. During the cold of Jan and Dec 2010, most places in this area stayed above 30, except for some isolated pockets in Pinellas Park and Largo, furthest from the water. But those were also not typical winter conditions, as most winters that doesn't happen. As far as just looking around and seeing what grows where, the map seems fairly consistent with my observations. At least I think it's a huge improvement over the previous map, which didn't even acknowledge the difference between Tampa at St. Pete.

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I saw more damage in Largo and Pinellas Park than my area of south Tampa in January 2010. Royals are zone 10 palms. How many big ones do you see in Largo or Pinellas Park that weren't planted in the last 5 years? How about some big Banyan trees? My office in Azalea Park, near Tyrone Mall, has a thermometer outside and it read 28F on January 11, 2010. My coworker in Seminole recorded 26F on his back porch that same morning. Mike Evans told me he recorded mid 20's at his Bay Pines garden. This indicates widespread cold not isolated pockets. Largo and Pinellas Park are good sized areas not isolated pockets. The only areas of Pinellas to stay above 30F that morning were within two miles or so of the water or maybe under a dense oak canopy. You're right, this doesn't happen every year. When it does however, the results are always the same. The central peninsula gets hammered while coastal areas go unscathed.

Placing all of Pinellas into zone 10 is almost as silly as making all of Hillsborough zone 9. The spine of the peninsula is too far removed from the Bay or Gulf to enjoy the water induced microclimate. Those areas are consistenly 2-4 degrees colder than the St. Pete-Clearwater Apt temperature and 4-6 degrees colder than Albert Whitted. Old Northeast St. Pete and Bryan Dairy Road are not in the same climate zone.

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Royal palms are excellent markers because there's so many of them, and the nursery-grown trees seem to be fairly uniform. In my area, the 1989 freeze destroyed most of them, but there's some impressive survivors. Massive planting over the past decade is setting the town up for huge losses. I think Archontophoenix cunninghamiana may offer a bit more hardiness. Apart from that, the December 2010 freeze made it clear what's long-term in my yard, and what will eventually be removed.

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As I stated on another thread, with respect to Highlands County, Florida, I feel the new map is generally correct, that the overall zone rating is 9b. The new map now shows the cold pocket in south central Highlands County as being zone 9a. In fact, there is an official NOAA station in this cold pocket located at Archbold Biological Station, and almost invariably they record sub 20 degree F readings once or twice each winter, which would actually make the zone rating 8b. On two ocassions, the last being January 5, 2001, ABS recorded a low of 13 degrees during a radiational freeze. I recorded 22 degrees at my place that morning and John Bishock recorded 22 degrees at his place in Old Mayakka. In January of 2010 I recorded my all-time open yard low at 20.8 degrees. ABS recorded 15 degrees that morning.

The only other thing I would add is that the zone rating around most of Highlands County lakes is zone 10, due to the thermal effect of the water. Lake Istokpoga (43 square miles) is definitely zone 10a, and in my opinion should show up (in representative color) as such. I've driven around this lake and found mature zone 10 palms and plants all around it. I took the below photos (and many more) three years ago. These were taken on the east side of Lake Istokpoga:

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Canal leading to Lake Istokpoga. Click on image below to view jumpy and grainy video taken in January of 2009:

th_royalspond.jpg

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If every winter has been as warm as this winter here on Pensacola beach I could start growing coconuts :lol: My ultimate low recorded so far has been 38 at the weather bug station down the street.

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Walt - interesting pics. How far away do you estimate the warming effect of the lake last? That's a heck of a micro climate with Coconuts thriving for an area that dips into the low 20s!

If every winter has been as warm as this winter here on Pensacola beach I could start growing coconuts :lol: My ultimate low recorded so far has been 38 at the weather bug station down the street.

Are you a few blocks from the water? Is it 9b-10a there??? 38 is much better than here in Orlando where many places saw around freezing twice this January, with many locations even a few degrees below. There are some double Adonidias near me with significant browning on the fronds. Maybe tomorrow I'll post a pic.

...by the way, on the INTERACTIVE MAP when I put my zipcode and shows Metro Orlando all I see is the 9b color. How do I get the 10a pockets around lakes/downtown to show up?

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Yeah I am a few blocks from the water. The map puts me at 9a and I think mostly is right. Where I am at we are definitely vulnerable to dips in the mid twenties on average winters but not much lower than that. This winter I believe it has hit 38 twice. Once in December and once right after new years. I have the slightest idea why the Orlando area had cooler temperatures... maybe from inland cold pockets or the direction the cold front was flowing.

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I saw more damage in Largo and Pinellas Park than my area of south Tampa in January 2010. Royals are zone 10 palms. How many big ones do you see in Largo or Pinellas Park that weren't planted in the last 5 years? How about some big Banyan trees? My office in Azalea Park, near Tyrone Mall, has a thermometer outside and it read 28F on January 11, 2010. My coworker in Seminole recorded 26F on his back porch that same morning. Mike Evans told me he recorded mid 20's at his Bay Pines garden. This indicates widespread cold not isolated pockets. Largo and Pinellas Park are good sized areas not isolated pockets. The only areas of Pinellas to stay above 30F that morning were within two miles or so of the water or maybe under a dense oak canopy. You're right, this doesn't happen every year. When it does however, the results are always the same. The central peninsula gets hammered while coastal areas go unscathed.

Placing all of Pinellas into zone 10 is almost as silly as making all of Hillsborough zone 9. The spine of the peninsula is too far removed from the Bay or Gulf to enjoy the water induced microclimate. Those areas are consistenly 2-4 degrees colder than the St. Pete-Clearwater Apt temperature and 4-6 degrees colder than Albert Whitted. Old Northeast St. Pete and Bryan Dairy Road are not in the same climate zone.

I just looked at the weather data from my station at my old house in Tarpon Springs (from which we just moved last month) and saw the following as yearly lows-----

2012 - 33.8F

2011 - 31.0F

2010 - 29.5F

2009 - 31.3F

2008 - 29.5F

2007 - 34.4F

2006 - 34.3F

So, there have been a couple of dips into the very high 20's, although the values would round up to 30F. As my house was ~1.5 miles from the coast, I think the map above is generally accurate in showing northern Pinellas as 9b. Maybe west of US19 is 10a but thats probably about it (and its got to be very hard for the folks who have to make these maps to account for all the warm and cold pockets.)

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Old Northeast St. Pete and Bryan Dairy Road are not in the same climate zone.

Aint that the truth. I personally think the area of downtown St Pete (Albert Whitted) is 10b as there are too many big old Royals, Ficus, etc, but its a fairly small area. And, its a "cold" 10b in that the daytime highs are a little less (sometimes a alot less) than a 10b down in SE FL.

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To show you what a range of temepratures can be found in the Orlando area...

Here at Leu Gardens the low so far for the winter is 35F and we have had 38F three times. This is exactly what the NWS station at Orlando Executive Airport recorded, it is just a couple miles east of downtown and a couple miles south of here.

I live north of downtown in the Collge Park area. Not sure what the exact low was in my area but it didn't drop below freezing. Bananas and elephant ears are still green and my Ficus lyrata in the open has no burn or damage. My girlfriend lives in Altamonte Springs (10 miles north of Orlando) in a colder pocket and has had below freezing a couple nights, lowest was 29F. The director here at Leu Gardens lives up towards Lake Mary (about 15 miles NW of Orlando) and has had down to 24F this winter.

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To show you what a range of temepratures can be found in the Orlando area...

Here at Leu Gardens the low so far for the winter is 35F and we have had 38F three times. This is exactly what the NWS station at Orlando Executive Airport recorded, it is just a couple miles east of downtown and a couple miles south of here.

I live north of downtown in the Collge Park area. Not sure what the exact low was in my area but it didn't drop below freezing. Bananas and elephant ears are still green and my Ficus lyrata in the open has no burn or damage. My girlfriend lives in Altamonte Springs (10 miles north of Orlando) in a colder pocket and has had below freezing a couple nights, lowest was 29F. The director here at Leu Gardens lives up towards Lake Mary (about 15 miles NW of Orlando) and has had down to 24F this winter.

Eric-

That sounds similar to areas of extreme NE Pinellas and NW Hillborough. I used to commute to Temple Terrace from Tarpon Springs, and on very cold mornings Ive watched my car thermometer drop 8-10F on the ride east. One morning I specifically recall it being 33F in Tarpon Springs and by the time I got to the Hillborough line (NE Pinellas edge) it was reading 24F! Thats ~1 USDA zone differential. On that same morning, SE Pinellas was reading in the lower 40's. Thats ~2 USDA zones differential! And one wonders why there are Banyans in SE Pinellas and Live Oaks in NE Pinellas.........

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Might have been the direction of the cold front which I think had sort of a more of an E-SE trajectory so your proximity to the ocean kept you at 38.

That's true, big difference in O-town temp range. The more concrete there is the better. Channel 9 near downtown was in the mid to lower 40s when many locations were hitting 32 and even lower last time.

A year ago, Roebellinis around my neighborhood were damaged but kept some green. While a mile or less east, I drove through a neighborhood where they were toasted.

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Walt - interesting pics. How far away do you estimate the warming effect of the lake last? That's a heck of a micro climate with Coconuts thriving for an area that dips into the low 20s!

The lake effect during calm cold nights (no wind) doesn't extend out too far. I would estimate all the effect is lost after about 800 -1,000 feet away. I only say this based on cold/frost indicator palms and shrubs I observe. During the severe radiational freeze of January 5, 2001, I noticed once I got within two blocks of a large lake, foliage damage started to lessen, and became less and less the closer to the lake.

However, the protracted cold periods of January 2010 and December 2010 killed many coconut palms, even nearer the lakes. I'd say maybe up to 50% of them (I believe more to duration of cold and not ultimate low temperature). Many, but not all, of the surviving ones haven't fully recovered yet.

What I discovered was tender palms growing on the highest ground here (up on the Lake Wales Ridge) seemed to fare better than those nearer the lakes (in January and December of 2010). I believe the reason for that is because the lakes, being relatively small as compared to the ocean and Gulf) gave up much of their heat, and by the end of the long cold spell the lakes' thermal effect was notably lessened. However, high ground areas enjoyed warmer air due to air stratification and warm air inversion layer.

The below Cocous nucifera are growing near Lake Grassy here in Lake Placid, Fl. (there are many more). These palms were hurt in January and December of 2010 as you can see them today on Google Street scene (photos were taken in early 2011 and the frond damage can be seen).

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The above coconut palms (as per the owner) were planted about five years ago. His son is a landscaper in Palm Beach County and trucked them over here and planted them. There are actually three palms and all have bent/swaying trunks (where grown and planted that way).

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The above three coconut palms are growing along side a narrow canal that leads to the east side of Lake Grassy. I spoke with the Cuban owners who moved up here from Miami 15 years ago. They told me they planted them as juveniles and that they have never been hurt.

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The above coconut was hurt during the prolonged cold of January and December of 2010, and is still recovering. There was a companion coconut palm that is now gone since I last photographed it several years ago, so I assume it was killed by the cold

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The above small coconut is on high ground and, based on its crown, doesn't appear that it was hurt too much from 2010 freezes. I know it wasn't hurt thus far during 2011/12 winter.

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This is somewhat similar to the map I drawn up back in 2010! This one is more accurate that past maps by far, but I still think mine was better.

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This is somewhat similar to the map I drawn up back in 2010! This one is more accurate that past maps by far, but I still think mine was better.

I think I recall you (someone) posting a zone map which showed shading around some of the lakes to indicate a one half or more zone increase vis a vis the surrounding areas. I recall I posted and commented I was in agreement with it.

From my personal observations, there is a one half to full zone increase around most of the larger lakes, with the southeast sides being the warmest and extending out the farthest. Further, the highest points on the Lake Wales Ridge are, IMO, just as warm as around the lakes during radiational cooling nights. This certainly proved to be the case during the long cold spells of January 2010 and again in December of 2010.

The below coconut palms are growing in the residential part of town (Lake Placid, Florida) about one block north of lake Pearl. They were cold damaged during the protracted cold period of January and December of 2010, but have since made almost a complete recovery.

2632839480042496162S600x600Q85.jpg

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The below coconut palms are at the Lake Grassy Motel in south Lake Placid between Highway US 27 and Lake Grassy. The motel also has lots of coconut palms planted along the beach (lakefront). All of the coconut palms were cold damaged from the cold 2010 weather, but have since regrown normally.

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I was in Lake Placid a week ago and managed to miss those coconuts.

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I was in Lake Placid a week ago and managed to miss those coconuts.

If you were driving north on US 27 (from the intersection of US 27 and Rt. 70, the coconut palms would be on the right hand side (east side) of US 27, maybe 3-4 miles north of Rt. 70 (at the Lake Grassy Motel). Just past the Lake Grassy Motel is an older lakeside subdivsion called Hickory Hills. One home owner has about a dozen large coconut palms in their yard. One is shown below (in front yard). All the rest are in back by the lake (where it's warmer).

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Another coconut palm (at different residence) in the Hickory Hills subdivision.

Out here in the deep inland there's no substitute for bodies of water and/or elevation on radiational cooling nights; it's worth a full USDA zone over the outlying areas.

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