N. rhabdothamnoides is the tree-like “gesneriad that you can climb” from Lord Howe Island. The plant in the photo, however, was only just over a meter tall.
The native climate on Lord Howe Island is cool and wet, which is how the Stewarts grow it. It is very intolerant of soil dryness, and wilts very quickly — it will come back, but with some leaf loss, if a wilt is caught quickly.
The pollinator is unknown, perhaps a bat.
It grows as a shrubby and branching small tree in nature, as can be seen here.