If you are in a hurry to start harvesting and do not want to wait for your trees to grow, you may buy full-grown trees. This would be ideal for a very small patch of land but extremely expensive in a sizeable orchard. For a substantial production, it is better to buy tree seedlings and nursery stock to make sure your production starts on the right foot. Adult trees grown from seedlings will be more resistant, bigger and yield more fruits than trees which will have grown to their full size in a container, to be bought and depoted into the ground. If you plan on having a reliable and profitable orchard, it is better to invest the time into growing your seedlings than buying grown trees.
Pollination is a critical stage in the lifecycle of the olive. Olive tree pollination occurs with self-pollination or cross-pollination. Usually, no outside agents are involved in the pollination of olive trees. Bees and wind may play a role, but they are not required for self-pollination. Cross-pollination requires wind as a dispersion agent.
Successful pollination require mild temperatures and a humid climate. Cold temperatures or dry climates will impair pollination. Although olive tree pollination is fairly self-sufficient and can produce a good yield on its own, some producers prefer to use pollinizers (also called pollinators). Pollinizers are agents which carry the pollen from the male part of the flower to the female part of the flower. Popular olive tree pollinators are other olive trees, such as the Pendolino, the Maurino, the Ascolano and the Mission. The use of these pollinators can increase pollination, although not all combinations of pollinator and olive tree type produce an increase in yield. Some pollinators can actually decrease the yield of a crop if used with the wrong kind of olive tree. They should be matched together carefully.
1) "Variety and Maturity - The Two Largest Influences on Olive Oil Quality" by Paul Vossen
2) Production Techniques in Olive Growing by the International Olive Council
3) Olive Production Manual by Steven Sibbett