Pachycereus
Pachycereus is a genus of 9–12 species of large cacti native to Mexico and just into southern Arizona, United States. They form large shrubs or small trees up to 15 m tall, with stout stems up to 1 m in diameter. "Pachycereus" comes from the ancient Greek παχύς ("pachys") meaning "thick" and the Latin "cereus" meaning "torch". Species. "P. pringlei" is the tallest cactus species in the world, with a maximum recorded height of 19.2 m. These genera have been brought into synonymy with "Pachycereus", although this is not always maintained: