Begonia nahangensis is another of a number of stunning, highly-bullate, species hailing from limestone areas in Quang Binh province, Vietnam. My limited experience growing it so far suggests it will responded well to the similar almost-closed terrarium type culture that suits B. melanobullata, B. ferox, and so many of the other rainforest understory species of this ilk. Like these others, I incorporate a roughly 3-5% ratio of limestone chips with my otherwise pro-mix based potting medium.
As is described as being found clinging to limestone cliffs & rock crevices in shade, suspect it will be somewhat wet-sensitive - so keep that in mind.
The foliage of B. nahangensis consists of raised black (melano) cones (bullae) that rather resemble teeth and are held on somewhat flat rosette of broadly orbiculate reddish leaves.
VERY limited number of these amazing plants are available. Offered here as husky young plants in 2 1/2 - 3" pots.
View Terrarium / Begonia Culture Sheet