(Edit: sorry about caps... I dont know how to correct it!)
Hi leatherback!
I dont have growing tips but I would like to share how I handle mine during the building process.
I do have a ficus that I am working on to build secondary ramification so not in the same stage of development as yours but the principle is the same.
To answer your question for me higher humidity will encourage aerial roots production.
From my experience, Plastic bag or anything to keep high humidity level is a usefull and proven tool to create aerial roots but not really to promote back budding.
Back budding occur because the tree is filled with energy, higher humidity after cutting can help alot with bleeding.
High temps are necessary with tropicals as mentionned already
The easiest way I found so far to encourage back budding with my tree is to let it run, simple as that!
I tried 2 methods on my tree actually, on the same day until today where I took pictures for you.
I wanted to solidify my knowledge on ficus so I had to do this experiment and see the results by myself.
I pinched tips on certain branches (only a few!!) and let the majority run just to see the differences.
Both method seems to work and encourage back budding but letting the branche grow and elongate without removing the tip brings results faster, healthier shoots emerge and once the desired back buds occur and the new branches starts to develop now you can safely cut back.
Here some examples:
The tree:
View attachment 439731
Here's an example of a shoot I let run.
You can see a nice little branches with short internodes forming lower down.
I dont want to reduce the main branche yet as Im waiting for a second branche to emerge before cutting.
If I reduce it right now to this new first branche I will simply end-up with the exact same situation.
View attachment 439732
Example here of a branche that the tip been pinched.
It is now creating new branches all along but look at their state of development compared to the previous one.
View attachment 439733
Another example that has been pinched.
Lot of new branches going out but the development is slow compared to leaving the branche as it is and come back when backbudding occured and is solid.
View attachment 439734
Another good example of a branche that I let run.
Secondary/tertiary branching are more developed.
I will come back soon and reduce the main branche to theses first 2 branches, one will be the new leader that will experience the same threatment, the lower one will be used as a tertiary.
View attachment 439737
exact same for this branche but this time I will be able to keep even more tertiary branches
View attachment 439738
I also found that removing older leaves on main branches can also promote back budding as seen here.
Tertiary branche (the small bottom one) has showed-up after I removed the leave there with the petiole leaving a scar on the bark but again the tip were not removed.
View attachment 439739
To resume:
Leave the branches grow untouched until you are satisfied with occuring back budding.
I would not remove any leaves at that stage, more leaves more opportunity of back budding.
Once there dont reduce to a newly created single branche as you will end up in the same situation.
Reduce to a minimum of 2 new branches and apply the same technique.
Let them grow as they want, let the backbud occur by itself and then come back to reduce to 4 newly created branches ect
Ive seen ficus that never develop because the owner always come back to a newly created single branche and remove the tip...
Growing is slowed down to a minimum,
the tree create a single new bud and elongation will start and he apply the same technique...
At this rate they will end-up with a tree that will not be refined after 20 years.
Pinching from my expericence will be only used when in refinment of the tertiary branching as it still promote back budding but it slow thing down alot.
Hope this help!
Ugo