Cave deposits from the Tehuacan Valley, near present day Puebla, Mexico, suggest that man's association with this plant began more than 12,000 years ago. Nevertheless, avocado originated in from protected mountain valleys and ecological regions in Central America, geographically separated from current areas of cultivation in the United States, such as Southern California.
Avocado pollination is complicated by several factors.
First, avocado flowers have a complex floral biology. They are protogynous. In some cultivars, stage I occurs in the morning of the first day and stage II in the afternoon of the second day, while in others, stage I occurs in the afternoon of the first day and stage II in the morning of the following day. However, temperature and humidity are known to strongly affect the reproductive cycle of flowers, so that stigma receptivity may be extended to stage II and flowers within the same tree may not open and close in synchrony. This extended period during which trees produce bloom results is a rather protracted harvest period, with pulses of maturing fruit throughout much of an average year.