I know from past experience that dried fondant decorations stick nicely to buttercream, cream chesse icings but I have to drape tree branching up all the tiers and dried wouldn't cut the mustard.  I will insert image of inspiration cake here.

I did the leaves fondant and gumpaste but am planning that same mix for the branches...yes? No? any insight here?

It cut off the first part of my question....how can I get the wet, moist fondant/gumpaste mix of branches to stick to the decorators recipe cream chesse icing?

Dampen the back of the branches/leaves with a little water to get them to stick, or put some of the CC icing in a pastry bag and pipe little blobs on where you want the branches to go.

Thank you for replying- I planned to wet my dried leaves, but did not know that a bit of water would help keep the fresh, moist fondant from sliding down the cake.

Only a tiny bit of water - use a damp paintbrush, or you do run the risk of them falling down and smearing the white cake with colour from the leaves/branches!