Citrus

The genus Citrus is native to a broad swath of South, East, and Southeast Asia — the Himalayan foothills of northeastern India, southwestern China's Yunnan province, Myanmar, the Indochinese peninsula, and the Malaysian archipelago. Citrus species began diverging from a common ancestor roughly 15 million years ago; domestication itself involved so much natural hybridization between wild species that scientists still can't pin down precisely when or where it first happened.

From its Asian center of origin, citrus spread into Micronesia and Polynesia via the Austronesian expansion (roughly 3000–1500 BCE), then reached the Middle East and Mediterranean around 1200 BCE by way of the incense trade route, eventually reaching Europe and, much later, the Americas.

Meyer lemon was collected in 1908 near Peking, China, by USDA plant explorer Frank Meyer, who vanished mysteriously on a later expedition on the Yangtze River in 1918. Decades later, growers discovered the original trees were symptomless carriers of citrus tristeza virus — California quarantined the original stock, and the virus-free "Improved Meyer Lemon" is the only version legally sold today.

Satsuma mandarins sparked what Gulf Coast locals in the early 1900s called "Satsuma Madness," after roughly a million trees were imported from Japan between 1908 and 1911 and planted across Alabama, Louisiana, Mississippi, and Texas — several towns are still named Satsuma today.

Kaffir lime is increasingly sold under its Thai name, makrut lime, after researchers traced "kaffir" to an Arabic word for "infidel," now recognized as an offensive term in parts of Africa.

The University of California released the virus-free "Improved Meyer Lemon" in the early 1970s, after identifying the original Meyer lemon stock as a silent carrier of citrus tristeza virus — a real, applied piece of disease-resistance breeding that saved the variety from being lost to quarantine entirely.

Key lime, the classic Florida fruit, was nearly wiped out commercially by the Great Miami Hurricane of 1926; growers largely replanted with the hardier Persian lime instead, and most "Key lime" flavoring sold today doesn't actually come from Florida-grown Key limes.