USDA Hardiness zone is not a good way to have a abstract view on minimum temperatures

[Estlander]

10 hours ago, Reynevan said:

Hardiness zone has changed also for my country ! It used to be 6a for bigger part of country, then 5 in mountainous region, 7a near the sea. Now it all raised by one degree !  
https://www.plantmaps.com/interactive-poland-plant-hardiness-zone-map-celsius.php

As it has also for my country of Estonia further north of you. And i see one area called Hel in northern Poland is even 8B. Wow.

But what is even more amazing is that a norther half of an Estonian island called Naissaar is in zone 9A. That’s almost at latitude 60N.

That’s the same zone as where I live now in FL. 

Yes, winters in Estonia have become pretty mild. But almost every winter we do get a bad cold front coming through lasting about a week, where temperatures fall in the -15 - 25C range. Hard to believe Naissaar staying within zone 9A temperatures during those cold spells. 

Edited August 23, 2018 by Estlander

[bubba]

What grows and flourishes.

[mdsonofthesouth]

On 12/30/2010, 9:23:57, bubba said:

USDA Zone system analysis is an extremely poor measure for determining the viability of a tropical/subtropical Palm as well as most tropical vegetation.For example, a climate that remained a constant temperature of 40F would be classified Zone 11 USDA.Can a Coconut Palm grow in this climate? Of course not. That stated, Coconuts are regularly posted on this Board in Orlando (19 F)and Brownsville (12 F)that based upon all time minimum temperatures qualify as Zone 8 USDA.

 

The USDA is a flawed system that at best gives a very basic overview on climate. It does not take into consideration the variety of climate assessed. No distinction is made between Med., Desert or many other varieties that take into account accumulated heat as well as higher average temperatures.

 

The Koeppen Classification has always been a more accurate indicator for "what grows" in Florida.It's reliance on the average minimum temperature in the coldest month equaling 64F or higher as the commencement of the tropical designation seems to go hand in hand with the area where the coconut grows. The coconut is the leading index for your entry into the tropics.

 

This is my thought exactly! Think of Banana Joe, he lives in BC Canada and talks about z9 all the time, but to me it gets downright cold in summer time sometimes dipping into the low 50s. and sometimes the highs are also in the 50s and 60s like today. That zone 9 is a far cry from a Florida or Texas or California zone 9. The other side is a zone 7 where I live where most winters are zone 8+ temperatures and rarely do we see our actual classification. I look at USDA hardiness zones as a guideline and just 1 of the many factors in determining weather. We live where the geography limits the cold a little and we are milder than surrounding areas in winter due to the geography, although we retain the same USDA classification. I dont know the science behind it, but my neighbor explained it roughly when we moved in as it was why he chose here too! 

 

So many nuances to deal with.

[kinzyjr]

On 12/29/2010, 9:55:09, _Rich said:

I've got moderately comprehensive Excel spreadsheet (270 species) compiled by Larry R. Noblick from Montgomery Botanical Center and Fairchild that denotes varying survivability stages in temperature (degrees Fahrenheit)by species. If anyone is interested in this, please shoot me a PM with your email.

Rich

 

On 5/11/2018, 1:47:04, beliz1985 said:

Who has still got that excel spreadsheet by @_Rich? :) 

Anyone interested in the information referenced by @_Rich and @beliz1985 can find it in two tables here: http://www.bg-map.com/noblick.html

Additionally, if you would prefer the information in spreadsheet format, I've attached it to this post.

201808240000_LarryNoblickColdHardiness.xlsx

[Sandy Loam]

I am bringing this thread about climate maps back to life.  It was ongoing from 2010 to 2018 and contains lots of useful information.

In other threads, I have seen people express a preference for plantmaps.com as a superior reference to USDA cold hardiness maps or others.  I note that plantmaps.com uses the same hardiness zones as USDA, but it is significantly different from the USDA maps for the same region.  I have compared USDA maps to plantmaps.com for Southern California and they are quite different, particularly in the greater Los Angeles area and outlying regions.  I wonder which one is more accurate.  Does anyone have an opinion?

I have tried the Sunset zone maps too, but I find them confusing.

 

[kinzyjr]

5 hours ago, Sandy Loam said:

I am bringing this thread about climate maps back to life.  It was ongoing from 2010 to 2018 and contains lots of useful information.

In other threads, I have seen people express a preference for plantmaps.com as a superior reference to USDA cold hardiness maps or others.  I note that plantmaps.com uses the same hardiness zones as USDA, but it is significantly different from the USDA maps for the same region.  I have compared USDA maps to plantmaps.com for Southern California and they are quite different, particularly in the greater Los Angeles area and outlying regions.  I wonder which one is more accurate.  Does anyone have an opinion?

I have tried the Sunset zone maps too, but I find them confusing.

In my case, both plantmaps.com and USDA list my location and the areas around it as 9b with a previous zone assignment of 9a.  The Sunset Zones describe conditions in more detail; a level of complexity that does add to some confusion.  Overall, the zones describe what they are intended to describe.  My preference is to search out other information to develop a more complete snapshot of gardening conditions, rather than just climate, for an area.  For example, Trachycarpus and Jubaea tend not to do well in central FL zone 9b, but will happily take a coastal California 9b.  Whether it the consistent high heat and humidity or the nematodes in the soil, they have their issues in most places. 

Differences don't necessarily have to happen because of a large distance or a mountain range.  In my case, my soil is completely different than the eastern side of the county.  Mine is rich and dark, while some of the growers in Winter Haven or Lake Wales have sand with next to no nutrients.

It would be extremely difficult to create a zone system that takes into account the entirety of growing conditions (average high and low temperatures, record high and low temperatures, average/high/low rainfall and atmospheric humidity, soil type for a particular parcel of ground, average/high/low number of and dates of freezes, trending diseases in the area, etc).  It's probably easier to use the empiricle and anecdotal evidence available on the internet, this site in particular, to make an informed decision on what and where to plant and note the results.

[GottmitAlex]

The only way to really find out if it will grow there, is to try it. 

(Within reason of course) 

[Jimbean]

On 4/18/2019 at 11:47 AM, Sandy Loam said:

I am bringing this thread about climate maps back to life.  It was ongoing from 2010 to 2018 and contains lots of useful information.

In other threads, I have seen people express a preference for plantmaps.com as a superior reference to USDA cold hardiness maps or others.  I note that plantmaps.com uses the same hardiness zones as USDA, but it is significantly different from the USDA maps for the same region.  I have compared USDA maps to plantmaps.com for Southern California and they are quite different, particularly in the greater Los Angeles area and outlying regions.  I wonder which one is more accurate.  Does anyone have an opinion?

I have tried the Sunset zone maps too, but I find them confusing.

 

This is something that I took a big interest in myself.  What it comes down to is, what criteria is used in defining the zones, and what data is being used to define them; all with the goal to provide a picture of information that interprets the data accurately.  

The problem that I had with USDA zones is that there is a disconnection between what plants are defined as a certain zone, how the zone is defined, and the purpose of defining a given area a particular zone.  For example, royal palms can survive to a minimum of roughly 23F, and survives without damage to 28F.  It is therefore rated as a zone 10A plant (30F to 35F).  A zone is defined officially as the average of the annual minimum temperatures of the last 30 years of a location, without taking into account the all time record low (how cold it could actually get in that location).  You get a location, such as Merritt Island, which has a 30 year minimum average of 34F, but with an all time record low of 21F.  Technically Merritt Island is a zone 10A, but royals are far more likely to be killed in 21F than survive.  

So now you have three options:

1.) Explain that a royal palm does will not always survive in zone 10A as a result of cold weather, which defeats the whole purpose of the system.

2.) Define the zones differently than the 30 year minimum average.

3.) Change how plants are rated, like changing royals to a 10B palm instead.

I chose to define the zones differently.  I take an estimate of a 100 year average, and subtract 5F, making places like Merritt Island to be 29F in the long term in order to take the record low more into account.  For this I get criticized for making my estimations of zones as too conservative.  In Merritt Island, you can see ficus trunks wider than my car, coconut palms that are more than 35ft tall, and plumerias that grow above 20ft, and I rate it as zone 9B.  

That is also how I approached the zone 10A plants in Orlando thread.  I commented that Orlando is a warm 9B with a few 10A plants here and there.  They only achieve the sizes that they have because it has not gotten too cold since 1989.

 

 

[palmsOrl]

It may not get to that cold in Orlando again.

Of course, I wonder what the situation would be when a 250 year,  500 year, 1,000 year freeze occurs.

A 1,000 year freeze could drop Orlando to 11F without the area being developed and 16-17F with all the urbanization.  This is just (maybe realistic) speculation of course.

Thus, a 100 year freeze is about 18F in Orlando, but with the city here, it may be 24F instead going forward.

Heck, even Jan. 2010 (not a 100 year freeze) only reached 28F officially in Orlando.

[Jimbean]

2 hours ago, palmsOrl said:

It may not get to that cold in Orlando again.

Of course, I wonder what the situation would be when a 250 year,  500 year, 1,000 year freeze occurs.

A 1,000 year freeze could drop Orlando to 11F without the area being developed and 16-17F with all the urbanization.  This is just (maybe realistic) speculation of course.

Thus, a 100 year freeze is about 18F in Orlando, but with the city here, it may be 24F instead going forward.

Heck, even Jan. 2010 (not a 100 year freeze) only reached 28F officially in Orlando.

2010 was noteworthy, more on par with 1977 than 1989.

I calculated the heat island of metro Orlando to be just over 2F, not 6F or 7F.  Over the last 30 years, Stuart and Orlando have warmed by roughly 2F, and other major metro areas have warmed by about 1F.

[palmsOrl]

Perhaps Jim.  It just seems that with the amplitude of the extreme cold by other measures, it would have lowered temperatures below the upper 20s F as far as the extreme lows in Orlando proper.  My parents house in Maitland hot 24F and mid 20s at least 2 nights in January that year alone.  I was out of town in December.

[palmsOrl]

I suspect the heat island has warmed substantially, or we would have seen upper teens-low twenties officially downtown at least once since 1989.

[Jimbean]

33 minutes ago, palmsOrl said:

I suspect the heat island has warmed substantially, or we would have seen upper teens-low twenties officially downtown at least once since 1989.

This is all very interesting topic to think about.  One of the problems is that there is a lack of data, so there is a lot of guess work that goes into it.  

When I did the research, I took into account all data that was available so that I could take as much of the guessing out of it as possible.  Then I took into account the local topography as well.  This is a topic that I can talk a lot about, and I would be glad to talk about.  The problem is, is that I genuinely don't have the time to do an accurate map and explanations of what has happened over time.  I thought about do a video map of how Florida has changed year by year, but that would take days to do.