annual precipitation is 30 inches or so, right?

It is more than 30 inches...about 35 inches according to weather datas!

uhmmm I'm searching for more datas but they are discordant, anyway, it is surely more than 27.5 inches!

Pecan trees here in Z8 Texas like bottom land that is well-drained. Rainfall here is 32" average. East of me, the diseases are more of a problem and disease resistance is very important. West of me drought tolerance is more important. You will need at least one tree from each type to insure good fertilization. Generally the smaller nuts are considered the better quality, but nearly everyone likes the larger papershell nuts better due to ease of shelling. The Cheyenne variety has been raised around here and is generally liked. Attached is a nursery website with additional information : http://www.womacknursery.com/index.htm

Thank you scotjute!
I read that Cheyenne is a wake tree, brittle and it grows not a lot.
Is it true?
I'll buy one Kiowa, but i don't know if I have to buy a Cape Fear or a Cheyenne!
I would like to know a USA climate closer to mine to buy the cultivar they cultivate there...

The main limitation of your climate is lack of summer heat. The best growing areas in USA average 35C high temperatures and 20C low temperatures during summer. As a result we don't grow pecans in areas with mild summers like yours. That makes it hard to give variety recommendations. I'd think shorter season varieties like Pawnee and Kanza would suit your mild summers better. Those may not be available in your area.

Cheyenne has good nuts in this area and survives some pretty bad weather.

Pecans need lots of water or nuts are poorly filled. Same result if not enough heat. You may be growing shade trees, not nut trees.

fruitnut, are you kidding me?
Pecans grows well in North Carolina, where, as I can see there is not a very hot summer, maybe my summers are hottest than NC summers!
There is a commercial orchard at not more than 200km southern and another one at about 300km northern than me in Italy!!!
So that Pecans can grow there is totally true!
We are talking about Pecans, not Pistachios!
Pecans can be grown among 5 to 9 usda zone, so it can't be cultivated in hottest summer.
I live in a 9a or 8b zone, so there are not a lot of problems about summer heat.

I read Pecans needs 2000 heat hours, I have about 3600 heat hours, so no problems!

hereistay:

USDA zone tells nothing about summer heat. Zone 8 in coastal Washington state has way less summer heat than zone 6 of north Texas.

What base temperature are your heat units? What are your average summer high temperatures?

Pecans are native to Texas. It's our state tree. Average summer high temperatures are 35C.

We have an average of 29ðC.
I know that it's the Texas state tree but I read that it is cultivated also in NC and Georgia.
I read that in NC and Georgia there is a temperated climate and there are not very hot summers.
I calculated chill hours and heat units by using standard formulas and I had these values.
Anyway I didn't read that Pecans need so many heat units and different Texan farmers and the Georgia University, contacted by me, told me that mine could be a good place to grow Pecan.
Anyway, as a friend of mine tells "agriculture books can be rewritten in 50 years by a only man", namely, only if you try you can say that it is that way!
So, I don't mean to build up a commerce of pecan in Italy but only I want to have few nuts for my family.

NC and Georgia are a little hotter in summer than 29C. But you have a long frost free season and are warm enough to give it a try. Your climate is similar to that on the central coast of California say San Luis Obispo. That's not commercial pecan country. In California they are grown further inland where summers are as hot as Texas.

For example, in Southern Italy (but not in the dyest and hottest place in Italy), there is a commercial orchard, they cultivate only Shoshoni, Kiowa and Wichita, they have an average max temperature during summer of 31ðC, 2ðC more than me...would 2ðC make the difference?

2C won't make enough difference to matter for home production. Wichita is grown near here often with Western Schley also called just Western. The later is known as a reliable producer under difficult conditions.

Whether you can grow - and fruit them - successfully in your spot, I do not know. Nor, do I know how much of a problem, if at all, pecan scab disease is in your country.
But...due to scab susceptibility, none of the varieties you've named would be great choices for a home or low-input planting. If you have the equipment available for scab-control spraying, that's another matter.

On the pollenation issue - pecans are dichogamous; both male and female flowers are present, but at different times. You need a mix of Type I and Type II (protandrous and protogynous) varieties. Planting only members of one group will assure poor to no nut crop.

@ fruitnut: Wester is a rielable producer under difficult conditions?

@lucky_p: Yes I know, in fact Cape Fear is a Type 1, Kiowa a Type 2.
Unfortunately in Italy we have only Cape Fear, Cheyenne, Kiowa, Shoshoni and Wichita.
I forgot a nursery sells also Wichita, but by seeing the pollination pattern I excluded it.
Than I read that it is subject to Scab.
Is Wichita better than Kiowa?
Anyway I have struments to spray treatments and I have a patent to buy eventually chemicals.
Here we use to treat only grapes but we don't use to treat olives and other fruits.
We have a lot of Juglans Regia, the common nut, but we don't use to treat them and they are usually native plants or seedlings.
I have 4 big plants, I never treated them and they make good nuts.

Lots of varietal information at the USDA pecan breeding website, linked below, including susceptibility to pests/diseases; applicable for US growers... Italy... I don't know.

Most home growers do not have access to 'airblast sprayers' - but commercial orchardists, etc. might have one like this...
http://www.youtube.com/watch?v=96QoHL_4s0I

Here is a link that might be useful: USDA Pecan Breeding

I have something like this:

https://www.youtube.com/watch?v=p75q-A7gPAE

this one model is produced in my city.

Pecans grows well in North Carolina, where, as I can see there is not a very hot summer

They don't even get snow in the winter, it's blazing there! OK, they may get a 1/2 inch that melts in a day once in awhile.
It's hot there, now where I'm at, that is cool.
I thought of retiring in NC as the weather is awesome.

That'll work!

Drew:

I won't call NC weather awesome. I'd be more on board with blazing hot and sticky humid. No doubt the winters are better than the snow belt!!

Drew51, here too we have a bit of snow, not all the years but after 1 or 2 days it goes away.
I'm 26 and I only remember 2 great snowfalls but they are were the exception and during those years we had problems with citrus that are very sensible to frost and starts to have problems with a temperature of 4ðC (39.2ðC).
I read that pecans can resist until -10ðC (14ðF) or more, is it false?
If 14ðF is true I have no problem, never had lower temperatures!

Pecans if fully dormant and depending on rootstock are hardy to as low as -20F. In Texas hardy to at least 0F. We were 18F this week!