Question: What is the capital city of the least populous nation where Himalayan Butterfly Bush grows?
Sentence (from "Bhutan"): Bhutan ( ; འབྲུག་ཡུལ་ "druk yul "), officially the Kingdom of Bhutan (འབྲུག་རྒྱལ་ཁབ་ "druk gyal khap "), is a landlocked country in South Asia.
Relevant evidence: Yes