Actually, all you need to do for a lemon tree is plant it in loose soil, water the soil lightly, and stick it in a ziplock bag. See this thread: http://forums2.gardenweb.com/forums/load/trees/msg111341588777.html That lemon tree is mine. I grew from seed. All I did was (STEP BY STEP leaving out absolutely NO information) 1) I grabbed the seed from a lemonade drink made from a lemon bought from a lemonade stand, this past summer 2) put the seeds in a cup of water. All of them sank(sadly, I have no clue where they are now) 3) Placed them in a container somewhere (except for 6) 4) took that plastic cup and cut some holes in the bottom 5) put soil (which turned out to be harder than rock when watered) inside the cup 6) stuck the seed in the cup 7) watered the soil lightly 8) stuck the seed in a plastic ziplock baggy 9) put it on the counter 9) Forgot it was even there About 2 weeks later, I said "OH CRAP! AM I TOO LATE? IS IT DEAD? I CAN'T BELIEVE I FORGOT ABOUT IT!!! OH MY GOSH, PLEASE DON'T BE DEAD! PLEASE DON'T BE DEAD!!!" After panicking and looking for about 20 minutes, I finally found it buried under a lot of crap. I looked into the bag and I'm thinking, "Awwwwww!!!! It's so cute!!!" There was a little lemon tree with it's first two leaves sprouting. After I saw that, I stuck it in the windowsill where it's currently working on it's 5th leaf while finishing up it's 4th. It's the most beautiful thing ever. I would've increased the germination rate though to all six seeds instead of 1 of 6 if I had followed the directions provided online though(nick the seed coat and all that other stuff). But really, just planting the seed and forgetting about it for about 1-2 weeks seemed to work fine. I probably just got lucky though.

Hi Giacamo, those little green citrus sound like the 'calamansi' here in the Philippines. They are picked small and green, but if left on the tree they will go yellow inside, and eventually the skin will go orange - but Filipinos prefer most of their fruits under-ripened, or totally green! I've not been to Cambodia, but have been to Thailand a few times, and the climate here is very much the same. Minimum temperature I've experienced here was +24 C, and it felt really cold!! We do have lemon trees that grow here, but nobody knows what variety they are. I'll be buying one when I come back from Australia in February or March. I'd be happy to send you a few cuttings if your are up to grafting? Or some seeds, but there is a great risk they won't fruit to type, and you'll have to wait several years for them to bear fruit. As others have commented, for rootstock use local species grown from seed. e.g. Kaffir Lime. Seedlings of local species are the best in my opinion.

I don't know of the 'bush lemon', is it of the citrus family? Might be able to assist if you could id it.

I posted a message on the Cornucopia forum but this forum may be more appropriate. I am living in Phnom Penh but I am happy to pay for all postage costs.