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how to calculate cold hardiness zone


greekpalm
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How do i calculate my hardiness zone ? Is it the lowest temperature ever recorded ?

Is it the average of the annual lowest temperature ?

Is it the median of the annual lowest temperature?

USDA Hardiness Zones 9b to 10a

AHS Heat Zones 8

altitude 100 meters (320 Feet)

4 km (2,4 Miles) from the Mediterranean

16716.gif

lowest ever recorded temperature -4 C (24 F)

maximum ever recored temperature 45 C (113 F)

mean minimum temperature January 7 C (44 F)

mean maximum temperature January 14 C (57 F)

mean minimum temperature July 23 C (74 F)

mean maximum temperature July 33 C (92 F)

average annual rainfall 330mm (13 Inch)

average annual sunshine 2800 hours

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First, consider what type of general climate you are in. In your case, you are in a Mediterranean climate. Second, consider all data and climate maps that you can find for your area or even similar area. Third, refer to people that live in Mediterranean climates that know a thing or two about cold hardiness.

I know little about Mediterranean climates, but I could go on about the subtropics.

My two cents.

Brevard County, Fl

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I have all the data I need (temperatures) but as a general question ... which of the 3 above is applied to find USDA Hardiness zone

USDA Hardiness Zones 9b to 10a

AHS Heat Zones 8

altitude 100 meters (320 Feet)

4 km (2,4 Miles) from the Mediterranean

16716.gif

lowest ever recorded temperature -4 C (24 F)

maximum ever recored temperature 45 C (113 F)

mean minimum temperature January 7 C (44 F)

mean maximum temperature January 14 C (57 F)

mean minimum temperature July 23 C (74 F)

mean maximum temperature July 33 C (92 F)

average annual rainfall 330mm (13 Inch)

average annual sunshine 2800 hours

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I'm fairly sure it's based on averaging your lowest annual temperatures.

My closest reliable weather station doesn't have records going back before the year 1999, so I only have 11 years to work from. Here's what my numbers look like.

1999-2000 = 27 F (-2.8 C)

2000-2001 = 30 F (-1.1 C)

2001-2002 = 28 F (-2.2 C)

2002-2003 = 36 F (+2.2 C)

2003-2004 = 30 F (-1.1 C)

2004-2005 = 32 F ( 0 C )

2005-2006 = 30 F (-1.1 C)

2006-2007 = 25 F (-3.9 C)

2007-2008 = 30 F (-1.1 C)

2008-2009 = 34 F (+1.1 C)

2009-2010 = 35 F (+1.7 C)

Average = 30.6 F (-0.8 C)

Like you, I consider myself to be riding the fence between Zone 9B and 10a. Because I'm close to the coast, even when I experience temps below 32F/0C, it is rarely for even an hour. This translates to very little damage to the 10A tolerant palms I'm growing.

Zone 9b/10a, Sunset Zone 22

7 miles inland. Elevation 120ft (37m)

Average annual low temp: 30F (-1C)

Average annual rainfall: 8" (20cm)

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See Terry, I think you're considered a USDA Zone 9B. It's not your average low, it's your ultimate low for the last 10 years or so.

Matt Bradford

"Manambe Lavaka"

Spring Valley, CA (8.5 miles inland from San Diego Bay)

10B on the hill (635 ft. elevation)

9B in the canyon (520 ft. elevation)

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oops, you're right Terry. What I typed above is completely wrong. I don't know where I got that....probably somewhere near my behind area.

Matt Bradford

"Manambe Lavaka"

Spring Valley, CA (8.5 miles inland from San Diego Bay)

10B on the hill (635 ft. elevation)

9B in the canyon (520 ft. elevation)

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so is it ultimate low ? (why 10 years if "climate" is measured by a minimum of 25 years) or avarage annual lowest temp. ?

Edited by greekpalm

USDA Hardiness Zones 9b to 10a

AHS Heat Zones 8

altitude 100 meters (320 Feet)

4 km (2,4 Miles) from the Mediterranean

16716.gif

lowest ever recorded temperature -4 C (24 F)

maximum ever recored temperature 45 C (113 F)

mean minimum temperature January 7 C (44 F)

mean maximum temperature January 14 C (57 F)

mean minimum temperature July 23 C (74 F)

mean maximum temperature July 33 C (92 F)

average annual rainfall 330mm (13 Inch)

average annual sunshine 2800 hours

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From Wikipedia:

"North American Hardiness Zones - Based on the average annual minimum temperature for a given location, the USDA map provides an easy guideline for categorizing locations suitable for winter survival of a rated plant in an "average" winter..."

Either way, I agree you have to factor in the possible repeat of a 10-20 year low.

Zone 9b/10a, Sunset Zone 22

7 miles inland. Elevation 120ft (37m)

Average annual low temp: 30F (-1C)

Average annual rainfall: 8" (20cm)

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How do i calculate my hardiness zone ? Is it the lowest temperature ever recorded ?

Is it the average of the annual lowest temperature ?

Is it the median of the annual lowest temperature?

It doesnt matter becasue by the time you figure it out, you will get slammed by record lows two years in a row.

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lol

Yes, The USDA hardiness zone map and criteria was made for temperate climates, not for subtropical or Mediterranean climates. I can say for subtropical Florida, you should take your average minimum and minus five degrees F.

Brevard County, Fl

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How do i calculate my hardiness zone ? Is it the lowest temperature ever recorded ?

Is it the average of the annual lowest temperature ?

Is it the median of the annual lowest temperature?

It doesnt matter becasue by the time you figure it out, you will get slammed by record lows two years in a row.

Hahahah. Florida got slammed big time.

I asked the question in another forum, and got some good responses. http://davesgarden.com/community/forums/t/1143964/

I still don't know how to find the annual minimum temperature info for my city.

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How do i calculate my hardiness zone ? Is it the lowest temperature ever recorded ?

Is it the average of the annual lowest temperature ?

Is it the median of the annual lowest temperature?

It doesnt matter becasue by the time you figure it out, you will get slammed by record lows two years in a row.

Hahahah. Florida got slammed big time.

I asked the question in another forum, and got some good responses. http://davesgarden.c...rums/t/1143964/

I still don't know how to find the annual minimum temperature info for my city.

here you are !!!

http://www.wunderground.com/history/airport/KSBA/2010/12/7/CustomHistory.html

USDA Hardiness Zones 9b to 10a

AHS Heat Zones 8

altitude 100 meters (320 Feet)

4 km (2,4 Miles) from the Mediterranean

16716.gif

lowest ever recorded temperature -4 C (24 F)

maximum ever recored temperature 45 C (113 F)

mean minimum temperature January 7 C (44 F)

mean maximum temperature January 14 C (57 F)

mean minimum temperature July 23 C (74 F)

mean maximum temperature July 33 C (92 F)

average annual rainfall 330mm (13 Inch)

average annual sunshine 2800 hours

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Another smart way to figure out what you can grow is to compare like species that you know will grow where you are to the Palmpedia Survivability Index.

http://www.palmpedia.net/wiki/index.php/MEDITERRANEAN_SURVIVABILITY_INDEX

Matt Bradford

"Manambe Lavaka"

Spring Valley, CA (8.5 miles inland from San Diego Bay)

10B on the hill (635 ft. elevation)

9B in the canyon (520 ft. elevation)

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Cold hardiness zones are just guidelines for what can be successfully grown in an area. The amount of protection you are willing to give and what amount of damage or losses you are willing to take should ultimately determine what you will plant. I'm in a colder area of Santa Barbara in a 9b zone. Many 10a plants will survive but are damaged most years. I like using bananas as indicator plants. Mine are brown but some of my neighbors are still green :(.

I believe the actual calculation is the average annual minimum temperature.

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The last official USDA map used a 12 year (winter actually) period for the average calculation. And the one they picked was one of the coldest on record (1974-1986). This resulted in the entire Eastern United States map being off by a zone or two. The USDA it is rumored is using 30 years for its new map, that was actually due last year, not to make the same mistake again. If you calculate the last 12 winters (even with the last one) for Miami Airport you get a solid zone 11, for the Sarasota Airport - a solid zone 10A. Take 20 years and it's still that. The 80's I didn't add, but with 20 years the average is solid enough to say that 4 cold years won't change it by much.

If a zone 10A range is 30-35F, then any plant classified as a Zone 10A plant could be counted on to survive that entire range if otherwise the growing conditions for that plant in that place are favorable. So if the Sarasota Airport's 12 year average is 32.5F (which is what it is), then the idea is that any drops below the zone range (below 30F) would be short enough to allow any plant that was classified to be counted on to survive down to 30F, to actually survive. In other words a coconut can certainly survive in the 30-35F range, maybe even below, but you cannot really count on it happen for the bottom part of that range below freezing, so the coconut should be regarded as a 10B plant and what this should mean is that it would probably survive in zone 10A most years, but not all. An Archontophoenix cunninghamiana for example can be counted on to survive the 30-35 range and is a zone 10A plant. And the certainty of surviving the bottom boundary temperature of 30F, gives it enough of a cushion to survive infrequent drops below that range.

I do agree with Matty though, the Palmpedia Survivability Index is at this point a much more useful tool.

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