This is especially true in the city of Salalah in the southernmost governorate of Dhofar, where frankincense trees grow wild. Before I even land in the sun-blasted seaside city, I get my first whiff.

Narrator: Frankincense is a milky white resin derived from Boswellia trees, which are remarkable for their ability to grow in unforgiving conditions. In fact, these trees have been known to grow ...