Tree fruits include temperate, subtropical and tropical zone species. Most temperate zone fruits are grown principally in regions protected from prolonged summer heat and severe winter cold (above −10 to −15°F or −23 to −26°C). The principal deciduous tree fruits grown in the United States are apple, peach, pear, plum, apricot, sweet cherry, tart cherry, and nectarine. Tree nuts, such as almond, pecan, walnut, and filbert, are sometimes classified as deciduous tree fruit crops.
Most subtropical fruit trees are evergreen. They will withstand temperatures somewhat below freezing during their dormant or semidormant season, but not the extreme temperatures tolerated by the temperate zone crops. Major subtropical fruits in the United States are the citrus group (for example, orange, grapefruit, lemon), olive, avocado, fig, and others of lesser importance. The Japanese persimmon might be considered as a borderline case between the temperate and subtropical zone groups, and avocado is often classed as a tropical fruit.
The tree fruit crops are grown commercially in orchards or groves, usually in single rows which permit necessary cultural operations for each tree. Nearly all tree fruit crops have similar requirements of training, pruning, spraying to control diseases and insects, and cultivation or chemical control of weeds.
