The olive branch has long been a symbol of peace, and the silvery-leaved olive tree has been considered sacred at least as far back as the 17th century B.C. Native to the Mediterranean area, the olive is a small oily fruit that contains a pit. It's grown both for its fruit and its oil in subtropical zones including the United States (Arizona, California and New Mexico), Latin America and throughout the Mediterranean. Olive varieties number in the dozens and vary in size and flavor. All fresh olives are bitter, and the final flavor of the fruit greatly depends on how ripe it is when picked and the processing it receives. Underripe olives are always green, whereas ripe olives may be either green or black. Spanish olives are picked young, soaked in lye, then fermented in brine for six to 12 months. When bottled, they're packed in a weak brine and sold in a variety of forms including pitted, unpitted or stuffed with foods such as pimientos, almonds, onions, jalapeños, etc. Olives picked in a riper state contain more oil and are a deeper green color.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.