When relatives visited Brighton Kaoma’s childhood home in the Copperbelt Province of central Zambia, they’d come bearing gifts: oblong brown chikanda, freshly dug from the earth of the family’s ancestral village. The tubers weren’t from yams or potatoes. Instead, they were foraged from the wild orchids that dot the dambos, or grasslands, of northern Zambia, their ornate blossoms shocks of color in the marshy knolls Kaoma’s family, who belong to the Bemba people of Zambia’s Northern and North-Western Provinces, would grind the tubers with peanuts and chiles, then boil them with water and soda to form a cake. Also called...