Funny thing is.. Mine was dumped to the gutter- true- by SF State. They did not want it and I was there to pick up other plants. I and my boss,a Professor quickly rented a truck and brought that back to the local U. It was mid winter,and the tree hadn't been watered for days to boot.
It was so big and heavy we could only yank it out of its box,cut off 1/2 or more of the rootball
It THEN sat for a few days in a college classroom after we brought it back like adventurers- lol,until we could get a big pot for this 12' tall tree.
Well,after all that...most of the top, died. We potted it up in that soil mix Colleges use all the time. Sunmix? Its been a few years. BUT..do you know that when longer days came around..it spouted not only new growth,but flowered. It actually had two pods on it when I found it in the street- how tough is that??-Those pods were cut open.mmmmm what an aroma. All the seeds germinated. Temps inside ran from a regulated to no higher, 80f to a low in cold winter days of about 60f. The rest of the winter and year closer to 70f for a low.
So I can tell you, any good quality potting mix with 25% Perlite is good enough. If you make your own out of shredded bark? I think it would do just as well...keep the roots moist,the humidity moderate,the soils airy. It was never steamy humid in that greenhouse..I would though hose the tree down when I watered it. Really a beautiful tree with its new leaves being thin and papery...much more then even a well fertilized Mango to give you an idea. To touch a leaf would tear it. Later..normal.
Seedlings are an easy grow really.
One warning- they are pest magnets. I couldn't use any kind of pesticide..so just hose that tree as best I could. Pesticide use would be up to you..I wouldn't know how fast a Bayer would wear off should you get a bloom..many years from now.
William,it was always a potted tree,I think it was about 30 years old,had a nice trunk and all that. But for SF State it was a reliable fruiter. I was told ants did the pollinating in their greenhouse. They had some tiny black tropical ant- no kidding- that not only did that,they also nested in the ant plants and the hollow leafed Cecropia plants of the SF greenhouse.
To this day,I sort of marvel at what was going on in that big greenhouse.