The grapefruit (Citrus × paradisi), is a subtropical citrus tree known for its sour fruit, an 18th-century hybrid first bred in Barbados. When found, it was named the "forbidden fruit"; it has also been misidentified with the pomelo or shaddock (C. maxima), one of the parents of this hybrid, the other being sweet orange (C. × sinensis).
These evergreen trees usually grow to around 5–6 meters (16–20 ft) tall, although they can reach 13–15 meters (43–49 ft). The leaves are dark green, long (up to 150 mm, 6 inches) and thin. It produces 5 cm (2 in) white four-petaled flowers. The fruit is yellow-orange skinned and largely an oblate spheroid; it ranges in diameter from 10–15 cm. The flesh is segmented and acidic, varying in color depending on the cultivars, which include white, pink and red pulps of varying sweetness. The 1929 US Ruby Red (of the Redblush variety) has the first grapefruit patent.
The fruit has become popular since the late 19th century; before that it was only grown as an ornamental plant. The United States quickly became a major producer of the fruit, with groves in Florida, Texas, Arizona, and California. In Spanish, the fruit is known as toronja or pomelo.