Tuesday, February 8, 2011

Zoned out

Do you know what zone you garden in? For most of us in Hawaii the answer is USDA plant hardiness zone 11. But that answer is based on the minimum temperature recorded each year in a given zone. And the minimum temperature counting stops at forty degrees. So if you live in Hawaii knowing your plant hardiness zone is kind of like owning snow skis. Not entirely useless, but close.

A few years ago i discovered another, better zone map. This one is the AHS Heat Zone Map and it explains things the USDA map never could. Things like why Jane's tomatoes don't do so well in August (but not why i can't grow tomatoes much at all). The idea is that plants begin to experience damage from heat when temperatures exceed 86 degrees Fahrenheit (30 degrees Celsius). Heat zones measure the number of days that this occurs each year.  


Viewing the map at 1600x i can see that tiny Maui, squeezed way down in the left hand corner, contains all twelve heat zones within its 720 square miles. Astonishing to be sure but no surprise to anyone that lives here.  Factor in rainfall and soil variables and it's easy to understand the lack of regional gardening advice.

The AHS map has really helped expand my gardening borders. Before i knew about heat zones i mostly paid attention to what was working for gardeners in S. California, Texas and South Florida. Now i know my garden resides squarely in AHS Heat Zone 5 so i also get to pay attention to what works for gardeners in places like northern Illinois and most of Oregon. Sort of ; )

Click here if you'd like to see what heat zone you live in.

9 comments:

Annelie said...

Yes, I do know, or so I thought. But before I started gardening I had no clue as to what a gardening zone was. I live in zone 6a (according to National Gardening Association. But looking at AHS map, I'm in zone 4 or possibly 5. Now I need to research some more to see what I can learn from this. Thanks for sharing.

Mr. H. said...

Hmm, I'm a little depressed now as we are in zone 4 maybe 5...brr.:) This is a very interesting map, thanks for sharing it.

Julie said...

Annelie we are practically neighbors then ; ) Always something new to think about, yes?

LOL Mr. H, if you start feeling down you just go right over and look at the mountains of food you grew last year! I can't see that you are in a hardship zone ; )

A Kitchen Garden in Kihei Maui said...

I have to agree that the zone 11 information is almost useless. I figured whoever drew up that map had never been to Hawaii! But this AHS map is very interesting - mahalo for sharing it. I didn't realize tomatoes don't grow well where you are.

Julie said...

Tomatoes grow like the weeds they are here Jane but the fruit flies are relentless. If i push beyond a few cherry or grape tomatoes it's just not pretty. The flies actually come into the house after the tomatoes around this time of year. Grr.

Pomaika`i said...

Wow,Julie, you come up with such great information! Now you have me thinking about setting up a little home weather station, to track the micro-climate at Pukalani. I don't get too much pilikia from flies, I think because they can't hang on at 40+ MPH "breezes".

Julie said...

Great idea!
We enjoyed a light and variable wind morning here today Barry, a rare treat.

Steve said...

Another useful climate zone model is one developed by the Food and Agricultural Organization arm of the United Nations. There model is based on what is termed the Potential Evapotranspiration rate (PET), which essentially measures the amount of moisture available in the soil for plant growth. In short, areas with a high PET value have a humid climate and long growing period and the opposite is true for areas with a low PET value. For example, areas to the south-west of the island of Jamaica have a low PET value and are suitable for growing tomato while areas to the north-east have a high PET and are more suited to crops like mangosteen. Overlay this with data on elevation above sea level and you can create quite predictable climate zones for tropical regions. I've been working on this for the past three years. iplantz01@gmail.com

Julie said...

Hadn't thought about PET in that way before Steve, but it makes sense. It's not easy to get reliable information about growing in tropical areas, probably because it's more profitable to study places where things like corn and wheat grow. Thanks for sharing.