Grapefruit

Grapefruit trees need full sun and cannot tolerate shade, growing best in a deep, well-drained loamy or sandy soil with a mildly acidic pH of 5 to 6, though they will also grow in neutral or alkaline soils with proper fertilization; the plant is sensitive to high salinity.

Watering: established trees are drought tolerant and should not be overwatered, since they perform poorly in waterlogged ground, but newly transplanted trees need watering every three to seven days at the base of the trunk to keep the root ball moist while they establish, with sandier soils requiring more frequent watering.

Propagation: because seedlings do not produce fruit true to type, grapefruit is propagated by grafting or budding onto rootstocks such as sour orange or rough lemon, and nursery trees are best transplanted into the garden in spring once the danger of frost has passed. Mature trees need little pruning beyond shaping and removing dead or damaged wood, and in cooler climates the tree can be grown in a container and moved indoors to overwinter.

Grapefruit shares many of the same insects and diseases that affect sweet orange, and it is highly susceptible to citrus canker along with several viral diseases, including crinkly leaf virus, psorosis, tristeza, xyloporosis, and infectious variegation.

Grapefruit ripens on the tree in fall and winter, and the fruit can be left in place through the winter to continue ripening and become sweeter, though doing so may reduce the size of the following year's crop.

Storage: once picked, grapefruit tastes best kept at room temperature rather than chilled.

Culinary: grapefruit is eaten fresh or juiced, and the juice is canned, dehydrated into powder, or frozen as concentrate; the fruit is also made into jams and jellies, the peel is candied for use in cakes, and the fruit serves as a source of pectin. Essential oil pressed from the peel is used to flavor soft drinks, chewing gum, sweets, baked goods, and ice cream, and it is also used in perfumery, while oil refined from the seed provides a culinary oil.

Traditional medicinal use: the leaves, flowers, and fruit of grapefruit have historically been used medicinally in some traditions, with a concentrate prepared from the flowers taken for insomnia, the fruit and its juice used to stimulate appetite and aid digestion or as a cardiotonic, the pulp employed for urinary disorders, and leaf extracts noted for antibiotic activity.

Grapefruit arose as an accidental hybrid of the sweet orange and the pomelo, both of which had earlier been brought to the Caribbean from Asia, and it was first recorded growing in Barbados and Jamaica in the 18th century. Seedlings were carried to Florida in 1823, and by the late 19th century grapefruit was being cultivated and sold commercially throughout the United States before production later spread to countries such as Brazil, Mexico, and Israel.