Citrus Growers Forum

ivica · Posted: Tue 09 Jan, 2007 9:16 am

Please, can you help me on this:

I'm living in the building where is the local weather report station, at
45.5° N 16.4° E. Googling I found that it is near border of zones 7 & 8.
http://www.gardenweb.com/zones/europe/hze6.html

My guess is that it is based on old data, maybe 1961-90, so I want recalculate my zone with more current data.

I can get data, problem is formula.
I have no idea which formula I should use Confused

Sorry for my english Sad

Best regards to you all!
--ivica

tomm · Posted: Tue 09 Jan, 2007 10:14 pm

Ivica:

Look at the temperature scale in Centigrade.
If last winter's lowest temperature was near -12,
then you are in 7b. If it was closer to -18, then your
Hardiness Zone is 7a.

The chart is made from average low temperatures
and is better for predicting the future
temperature than only one observation.

_________________
Tom Mortell

ivica · Posted: Wed 10 Jan, 2007 6:05 am

Thank you Tomm,

Meassured at 2 m above ground:
last winter's lowest temperature was -13 C, date 2006-01-26.
(and once in February temp was -12 C)

So, according to your suggestion my zone is 7b.

Just found:
"Climate Variables used to develop Canada´s Plant Hardiness Zones"
http://www.glfc.cfs.nrcan.gc.ca/landscape/ph_climate_maps_e.html
with formula having 7 climate variables X1..X7 and, confusing, 8 constants.

Any thought about constants, how they get that...?

Best regards.

tomm · Posted: Wed 10 Jan, 2007 11:11 pm

Canada's Forest Service hardiness zones are calculated
from more variables than the Unitd States Department of
Agriculture's hardiness zones. From the interesting
reference you gave, I see that they are using high and
low temperatures, amount of snowfall and rain and other
weather measurements.
If you have studied statistics you will recognize
"linear regression" (that is where they get the constants)
and "planar spline interpolation", which I have never done,
but it has to do with generating the nice smooth areas.
And if you realy know statistics you will exclaim:
"What, only 104 plants?"
USDA method is much simpler - average of the minimum
temperature for the previous 10 or 20 years.

After all that - "Plants don't read". Smile

_________________
Tom Mortell

ivica · Posted: Thu 11 Jan, 2007 6:52 am

Tomm,

I'm BSEE specialized for Computer Sciences but my math studies were years ago. I'm 46 years old.
What I want to do is:
1. Map hardiness zones, including microlocations, of my yard.
2. Calculate probability of survival for some specific citrus variety and location in the yard.

I'm not in a hurry and I'm not gonna plant any citrus in ground this year at least. We had no decent storm (wind or hail) for two years, I could get all that at once this summer I'm afraid Confused

Quote:

USDA method is much simpler - average of the minimum
temperature for the previous 10 or 20 years.

Event that is not clear to me. Trivialy evaluating local data I end up with mean temp being too high Confused

Quote:

After all that - "Plants don't read".

I'm accounting on that Smile

tomm · Posted: Thu 11 Jan, 2007 3:46 pm

Quote:

Even that is not clear to me.

For the USDA style hardiness zone you could:

Collect temperatures going back 20 years.
For each year, find the Year's Lowest temperature.
[ If Low_day < Low_YearN then Low_YearN = Low_day ]
Add up all the Low_YearNs and divide by the Number of years.
(I was going to write that in C++ with doubly indexed
variables, but I am much too lazy Smile

Read some of the postings about how people protect their
Citrus (and Cherimoyas) against freezes and you will
begin to understand the trouble you have to go to to keep
them alive. But then again, there are Citrus trees growing
in Germany and England, so you know it can be done.

_________________
Tom Mortell

ivica · Posted: Sun 14 Jan, 2007 6:58 am

Tomm,
Thanks to you I have now good starting point!
Evaluation of data confirmed 7b being my hardiness zone.
My play can start, I'm using Paradox for Windows - relational database & RAD tool.

Quote:

...Read some of the postings about how people protect their
Citrus (and Cherimoyas) against freezes ...

I'm lurking there already...
Best regards,
--ivica