Two trees were air-layerd (marcoted) in a south part of Bosnia and Hercegovinia (Dubrovnik hinterland) and brought here. That was 50+ years ago.
I was not aware of them since this year in spite of their current location (last 10y), 500 m from my place.

All photos taken September, 2009.
Photo 1: The trees

Trees A, B are 50+ years old, C is 10- years old (also air-layered).
The way how they are overwintered could be interesting, pink arrow on the photo shows their winter place. Polythene sheet (rolled, and visible on the photo) losely attached functions as south wall.
Minimal temperature last winter was -15.2 C but I saw no damage on the trees.

Photo 2: A few details


Photo 3: Leaves and flowers


Photo 4: Mamelon (a nipple at the fruit end)


Photo 5: 3y old fruits

In general, owner picks only 3 year old fruits (when they are of it's largest size, he says).

Photo 6: Cutted fruit

Thin skin, juicy.
Number of segments vary, here is 10.

Soil: Dirt from backyard, mostly.

Fertilizer: Pigeon droppings.

Cold Hardiness
Owner says that the trees should be cold hardy down to -7 degree Celsius.
That begs to be checked. Lets put that aside for a while. I'm preparing experiment which will have own thread, later.

Variety: Unknown
Please, make your guess.

Ivica, very interesting post. The owner says he only picks 3 year old fruit. I have never known, or heard of a lemon variety where the fruit remains attached to the tree without dropping for 3 years. Interesting- Millet (1,171-)

Millet, I was there today, visiting the trees and talking with owner.
What was meant with "3 year old fruit" is actually "fruit in its 3rd year".
He defines Optimal age as ~2.5 years.
Fruit of Optimal age can weight 300+ grams, photo of possible candidate (still young, one more regreening needed):


Realy 3y old fruit is in decline, like this one found still attached to the tree:


Comparing acidity of Meyer Lemon (~8 months old) and XXX Lemon (~2.5 years old):

Acidity is similar, one can eat such XXX lemon just like Meyer.

The Trees are under the roof last week but not in their winter position yet. Canopy detail of tree A:


Todays minimal temperature: -4C at 2m level, -6C at 5cm level.
Yesterdays minimal temperature: -3C at 2m level, -6C at 5cm level.

All photos taken today.

Interesting. Very cold hardy.

My Lisbon lemons get huge in just one yr--big as grapfruit--they do stay on for just over a yr in some cases--blooming in Feb/Mar and then staying on until the end of May the following yr--but at that point they fall off.

Skeeter,
Hardiness of those trees really intrigues me, look at this yesterday photos which shows their current (last week) position,
Trees A, C (facing east):


Tree B and 3 other citrus plants (facing south):


A week ago we had 3 consecutive days with a light frost, up to now we had 5 frost days. I saw no part of the trees A, B, C suffering from that.
There are more buds, flowers, fruitlets now then it was in September.

Other citrus plants (owner is not certain about varietes) are obtained from nursery 1.5 years ago.
1) A mandarin which have fruits for 2nd year in a row.
Tree looks good, could be Chahara Unshiu I think.
Chahara should sustain -10C for one hour.

2 and 3) An orange and a grapefruit, I'm not sure which one is what.
None of them flowered yet.
Young tips of the tree #3 already killed and blackened by cold weather.

It's snowing now.

I'd be interesting to see if any of these would root from cuttings next spring, as an experiment for instance.

Cheers, Barrie.

Barrie,
I did a few experiments already:
Rooted cuttings


Air-layered plants




Bark graft on inground P.T.

Ivica, very nice new little trees, are the rooted cuttings and the air layered trees from the 50 year old trees?- Millet (1,168-)

Millet, all trees A,B,C were used. No specific notes made, except that budwood, one rooted and one air-layered tree which I keep at my place have the C as origin.
I see now that I was not explicit in my introductory post, parent of the C tree is A or B tree.
All graftings, rootings, airlayerings I did in June, couple of weeks after I became aware of those trees.

Thank you, you did an excellent job. - Millet (1,168-)

Thank you, Millet.
For a years I wonder what citrus could be found in old backyards of Adriatic islands, coast, hinterland... Such research needs a lot of time and resources, basicaly I did nothing...

Then a lemon tree knocked on my door!

I'll do my best.
However, I'm not citrus expert and any suggestions are welcome.

> For a years I wonder what citrus could be found in old backyards of Adriatic islands, coast, hinterland...
Yes that would be a good job to do.
An other country to prospect would be Albany. their are many citrus there. Mainly orange trees.

I picked 4 fruits of different age for taste test today. The youngest had the mildest taste but nothing significant to report on that.
The suprise came cutting the youngest (<1 year) fruit, green seeds:



I did not never saw something like that and I don't know is that unusual or not.

Looking at the small size of the "grapefruit" and especially the fact that the fruit contains green seeds, plus the lower acid flavor, there must me some mandarin in the tree's heritage. - Millet (1,145-)

Mandarine heritage could also explain unusual hardiness.
Hardiness Test is ongoing, we shall know more by the end of January.