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zones do not incorporate summer heat levels into the zone determ

Posted by brooklyngreg 7A Coastal Plain (My Page) on
Mon, Dec 20, 10 at 16:29

We need to know our heat zone! See below!

The zones do not incorporate summer heat levels into the zone determination; thus sites which may have the same mean winter minima, but markedly different summer temperatures, will be accorded the same hardiness zone. An extreme example of this phenomenon is seen when comparing the Shetland Islands and southern Alabama, which are both on the boundary of zones 8 and 9 and share the same winter minima, but little else in their climates. In summer, the humid subtropical climate of Alabama is about 20 degrees Celsius hotter than the Maritime Subarctic climate of Shetland, and there are few similar plants that can be grown at both locations. Due to its maritime climate, the UK is in AHS Heat Zone 2 (having 1 to 8 days hotter than 30 degrees Celsius) according to the AHS (American Horticultural Society), whereas Alabama is in Zones 7 to 9 (61 to 150 days hotter than 30 degrees Celsius). Users need to combine the hardiness zone with the heat zone to gain greater understanding of what can be grown in a particular location.


Follow-Up Postings:

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RE: zones do not incorporate summer heat levels into the zone det

My heat zone is a 6. That means that I get 45 to 60 days of the year above 86F which is pretty close to right during the average year (but many summers are a little warmer than average.
Heat zones are very important in understanding a climate, but the one downside to them is that not a lot of people rate plants by heat zones (or at least I have a hard time finding their ratings). Some drawbacks are that a plant in full shade can handle a lot more heat than it can in full sun and also some more tropical plants will be burnt in the southwest and do fine in in Southern and Central Florida despite the fact that they have similar heat zone ratings (Florida rarely goes too much above 90F whereas parts of the southwest rarely go BELOW 100F during summer days!).
But if a map could be created that combines heat zones and usda hardiness zones, then it could give a pretty good idea of what you can grow in your climate! The map would probably be very similar to a sunset zone, only for the east coast instead!
Good luck!
-Alex


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RE: zones do not incorporate summer heat levels into the zone det

I think the sunset zones do include the east coast as well. I thought I have looked at them once somewhere? Anyway yeah the heat zone would be cool. Another example would be San Diego and Miami.


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RE: zones do not incorporate summer heat levels into the zone det

They do include the east coast, but it isnt really as efficent as it is on the west coast! I think Im in a sunset zone 32 (not 100% sure) which included most of New Jersey down into Maryland, Delaware, and Parts of eastern Virginia. But they have Long island as a zone 34 like most of New England and although summers are kind of similar to New England (especially the farther east you go) the winters in long island are milder and there are a lot of plants that will grow there that wont in most of New England (like southern magnolias and Camellias). All 3 of these zone maps together really would make one awesome climate map though!
-Alex


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RE: zones do not incorporate summer heat levels into the zone det

One of the problems I do see with the SunSet zones; at least for my area is that is puts it into a zone that need to be divided further. It also doesnt take into account how many days above 100f!!!


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RE: zones do not incorporate summer heat levels into the zone det

and most importantly of all (for palm growers at least) is zones do not include average daily temperatures. For example, the average daily temperature in my town in southern California in winter is probably in the 50s, while a town in Florida in the same zone (eg. Orlando) has daily averages about 20 degrees higher. Even though it may actually have some colder lows. So you can grow coconuts in Orlando but not here despite both being a zone 9b. Zones do not include humidity, either, another determining factor in what will or won't grow for you (which is why Juabaes do great in my yard, but not in my friend's yard in Orlando). There just is no way to create a meaningful zone system that would accurately help predict what plants will grow where.


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RE: zones do not incorporate summer heat levels into the zone det

Very true! Looks like the only way to truly know what will do well in your yard is by looking around your neighborhood and trial and error! And if a plant you like doesnt like your climate, then you just have to protect it and hope for the best!
Good luck!
-Alex


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RE: zones do not incorporate summer heat levels into the zone det

About a 120 days of 80 or higher here this year made up for any
damage cause by last winter,I think we had almost 90 in a row of 80 +.

It wasn't even a hot summer!

Click for Fairfield, Iowa Forecast


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RE: zones do not incorporate summer heat levels into the zone det

On the border of heat zone 4 and 5 here, so that's about 30 days a year of 86+. Normal highs hit 83F here or so in mid July. Perfect trachy growing weather in my opinion.

Now if I could do something about my zone 5b and turn it to a 7b and maintain heat zone 4 or 5. :)


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RE: zones do not incorporate summer heat levels into the zone det

Well,even Sunset doesnt seem to be in a rush to update its flawed system. Hayward Ca is not the same kind of zone 17 as San Francisco..much less fog,quite a bit warmer in summer than San Francisco..colder lows in winter-darn, can't have everything.
I think they could do a z17 as in San Francisco a z17b for the cooler farther north like Eureka and 17c for the southern and also patches of warmer northern SF bay area.


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RE: zones do not incorporate summer heat levels into the zone det

I think the chill factor could be a useful tool as either
part of the general description or as a side mark with other climatic stats.
Another possible thing they could do is add transition zones.

LOL now its getting complicated!


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RE: zones do not incorporate summer heat levels into the zone det

True,
Zones do not include average daily temperatures and I agree they should have some transition zones for plants like palms that include it.


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RE: zones do not incorporate summer heat levels into the zone det

Hi
Zone designations couldn't be more than a general indication could they?? I'm at the northern edge of 10
but live quite close to the sea so during cold fronts the low is often 10 degrees above areas 10 miles inland
Same is true for summer . Cold is a LOT more noticeable than heat though lol
Then there is the variation from year to year . This year for example set a record on daytime highs being 10/15
degrees below normal. So have had as many as 5 years in a row in 11 and 3 in 8 lol over a 30 year period. the rest fell into 10. This year will be a 8/9 at best lol gary


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