The scientific name of lemon tree is Citrus limon. Lemon trees thrive in USDA hardiness zones 9 to 11, and they grow up to 20 feet tall.
Lemons were probably created as a cross-breed of sour oranges and citrons. Lemons were grown in Italy as far back as the third century, and they were found throughout Mediterranean countries by 1150. Lemon trees first appeared in the United States in St. Augustine, Fla., and the trees arrived in California in the mid-18th century. Most of the U.S. lemon crop is grown in California, where 45,000 acres are devoted to lemon trees.