Mariel Tishma Chicago, Illinois, United States   Incense. Frankincense on coal. Photo: birdy. 2007. CC BY-SA 3.0. Via Wikimedia. Boswellia and Commiphora trees are scraggly, sharp, and unfriendly. Growing close to the ground in the arid desert, they have short trunks and fanning branches, sometimes looking more like shrubs than trees. But despite their unlikely…