"..If the hackberry is deciduous then you should start the air layer at the end of winter, right before it wakes up" I don't know where you got this info from, but it is not a very good idea. And will most likely not work at all. 1) If you air layer before there is foliage, there is nothing to provide the sucrose to develop roots. 2) If you "leave thin strips", the wound will just heal over, and not develop roots. "...this way it will still have some of the cambian layer to supply the upper portion," The cambium does not supply the leaves with anything. The cambium is the pathway for sucrose made by photosynthesis in the leaves, to travel to the roots. The inner core is the pathway up from the roots that supplies water and nutrients to the leaves. When we sever the cambium, water and nutrients can still reach the leaves who, who in turn send the sucrose developed (energy) back to the roots for storage (down through the cambium). Once this energy reaches the severed section of cambium, it has nowhere to go and collects there. This initiates the formation of roots at that spot. If the cambium is not entirely severed, there is still a pathway for energy to travel to the roots. And the tree will begin to heal the severed section while still functioning normally. It is a one way loop -

Pj, it sounded like you tried many methods but NOT air layering, which is well described on this site in other posts. In your case I would have taken cuttings, put them in barely moist towelling in a zip-lock and put them in the vegetable crisper of the fridge for a week. This puts them into dormancy. When they come out of the fridge, I would forget the baggie method for rooting and put them into a very well drained light potting medium (barely moist) in 16 oz plus clear plastic cups with drain holes. Put them on a warming tray covered with a plastic dome to keep humidity high. Your climate may already do both of these 'warm and moist' stages for you. When I do this method, I can usualy see good root development in a couple of weeks as well as budding and leafing out. Don't be in a rush to transplant, and remember that excess of water is a killer at this stage. Air layering works fine too, you just have to be patient, but you can do it anytime. However, it may take months for the branch to throw out roots, or just weeks. You could also try ground layering too if you have branches close to ground and can pin or weight them there for some time. My two cents... John.

I tried to google for some information how they compare to each other in the long run but I couldn't really find anything. I want to air layer some branches off maple trees but I had wondered whether they would perform as good as the grafted ones. Thanks

Figs are easily started from dormant cuttings, air layering would not be the easy way but if you want to try it you would want to start early in the year as it takes time to form roots. You would want roots well established before the new plant goes dormant. Al