I have an indoor orange tree - a small houseplant really (although it grows for about 18 years) - now, shortly, the problem is: even after two months the branch doesn't grow roots in the air-layered soil AT ALL. What must I do to really make it happen?

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Now some details:

I was reading some more in-detail stuff about air-layering a few months ago because I decided to try to reproduce my orange tree by such method (I knew about that method before - but never really *seriously* tried it - I just tried it once before with a plastic cup with hole on the bottom and cut so that it could fit around one small branch (0.5 cm in diameter) - but I never put too much fate that it would work).

As I said - now I really firmly decided to reproduce my orange tree using the air-layering method, and read stuff to make sure I am doing it properly. Anyway - this is how I did it: I took some wet houseplant soil (the commercial one for flowers and such, with coconut husk fibers in it or something), I put that wet soil in a saran wrap and then wrapped it around one fresh shoot on my orange tree (the shoot is about 0.5 cm in diameter and about 40-50 cm tall) - it's green and new - it doesn't have any real bark on it - so I thought I don't need to make a cut on it, wound it, or anything (maybe this is a problem - ? ), and then I wrapped the whole thing with some black cardboard so it hold the shape (the soil covers 10 cm in length and it's 5-6 cm in diameter) and additionally I wrapped the whole lot with aluminum foil so it is dark inside. I waited for three weeks at first and then looked at the results - nothing; I tried it again - after a month - even used hot water from the tap - nothing again - the branch looked as if I did nothing - clean with no roots whatsoever! So that's all (I know nothing about plant growing... never really considered using rooting agents... help).
It's winter now so I use artificial lighting on my little-old orange tree - both fluorescent and incandescent - that's why it's growing new shoots.

I really want to reproduce my tree - what do I do to make it really happen??
Many thanks in advance! :)

OK - time and patience - but if you or someone else here knows some surer method to make it happen - then I wish to know it - I want them as soon as possible - planted and growing happily - spreading them around - growing in the sunlight instead of inside rooms as the original plants all these years.

(Actually those are two orange tree plants in one container - grown from two seeds (directly from the fruit). I don't know if it tells something about the sort of orange - but my oranges have long thorns. They are really houseplants - maybe meter and a half tall.)

I guess - the straight question here on my side is:
Can a small 40 cm fresh orange tree shoot grow roots via air-layering to be planed in soil as separate plant?

Your branch is quite thin. I would use one 2-2 times that thick if possible. You can use the ring method, whereby you longitudinally remove ALL the bark from the branch for 1-1/2X the branch diameter, then finish your layer using moist sphagnum moss (not peat) or a very porous soil in a pot. If you need help here, just ask.

Alternately, if you plan ahead & put yourself on tree time instead of people time, you can wrap a few (3?) zip ties around a branch very tightly so they are touching each other. Wait until a bulge starts to form distal to the zip ties. When that occurs, wrap the zip ties and the first inch of bark above the ties with black electrical tape for a month (called 'banding') before you begin your layer. The black electrical tape eliminates light and 'blanches' the underlying tissue, causing physiological changes (reduces production of lignin, which allows phenolic metabolites to be channeled toward root initiation) in such a way that it enhances root formation. If you wish, before you layer, you can slightly wound the bark several times where the diameter of the bulge distal to the zip ties is greatest, and apply a rooting aid to the wounds and bulge.

Layer being used to shorten a tree to be used as a bonsai in the future:

Al

My ~great~ idea (I hope for it not to be a pipe-dream) was to both:
- regulate the height of my original house plant by air-layering any new shoots that go *upwards* (i.e. not sideways) and then cutting them off when they're ready to grow independently thus shortening the plant - because I want to be able to carry the plant around the flat (to the balcony (with tin roof above...) for the summers and inside during winters) and
- make new orange trees exactly from the ones I have - so it's two benefits at once - it all nicely adds-up - because I want to place those new orange tree plants somewhere outside for the summer where (under the full blow of the Sun) they would explode into action - I hope.

...I guess my next step will be to try to find some rooting agent and then try to apply it to the wound on the branch/shoot.

Would this work (and if not - why?):
Let's say I cut that orange three shoot off the tree and then make a lot of longitudinal grooves with exacto-knife at the bottom of the shoot to maximize the contact surface area - so it really soaks in those minerals from the solution - would it work?

...Or it's back to "...I guess my next step will be to try to find some rooting agent and then try to apply it to the wound on the branch/shoot."

PS: the strangest thing happened - yesterday (before I had that idea) while I was looking at a general direction of the plant out of nothing a word occurred to me for no reason: osmosis. Just a coincidence I guess. (back then I was just wondering how silly the word is :D (by the way now I see that it means 'ωσμος'='osmos' - 'to push', or 'implosion'))