By Harold McGee
Apple trees are especially hardy and are probably the most widely distributed fruit trees on the planet. There are 35 species in the genus Malus. The species that gives us most of our eating apples, Malus x domestica, seems to have originated in the mountains of Kazakhstan from crossings of an Asian species (Malus sieversii) with several cousins. The domesticated apple spread very early through the Middle East. It was known in the Mediterranean region by the time of the Greek epics, and the Romans introduced it to the rest of Europe. These days apple production is an international enterprise, with southern hemisphere countries supplementing northern stored apples during the off-season, and common varieties as likely to have come from Asia (e.g., Fuji, from Japan) as from the West. There are several thousand named apple varieties, which can be divided into four general groups.