As the centuries unfolded olives and olive oil became more and more important as staple foods. Through trade and conquest olive cultivation spread beyond its ancient and established boundaries and was successfully and abundantly cultivated, predominantly by the Spanish, in the different countries of the Americas as far north as California. Today, olives are cultivated in Australia and South Africa . The world's largest olive producer is Spain followed by Greece, Italy and Portugal. All olives will grow to a glistening black if left to ripen on the tree.
Green olives are young fruit picked at the first stage of maturity before they begin ripening.
The size of a green olive is determined by the type of tree from which it comes, not by how early it is picked. Extremely bitter and unpalatable when fresh, the young olives have to go through a curing process to achieve the bright and snappy flavour for which they are esteemed. There are three basic curing methods for removing the intense bitterness. The lye is removed by washing them in several changes of fresh water. A second and longer process is to steep the olives in brine for six weeks or so, changing the brine weekly.