James H. Schutte
CITRUS x paradisi 'Oroblanco' PP4645
Plant Common Name
Grapefruit, Oro Blanco Grapefruit
Large, pendent clusters of sunny, yellow fruit, reminiscent of grapes, give grapefruit its common name. It is a natural hybrid of the Asian pummelo (Citrus maxima) and sweet orange (Citrus sinensis) that was first described as the Barbados “Forbidden Fruit” by Griffith Hughes in 1750. The tree was later found on several islands of the West Indies, including Jamaica, and arrived in the United States around 1853 thanks to Odette Philippe.
Grapefruit trees are large, evergreen and sometimes have short, soft thorns on their twigs. The fragrant, thick, glossy leaves are broadly oval, dotted with small oil glands and usually have winged petioles (leaf stems). The flowers are born from late winter to early spring and may be clustered or solitary in the leaf axils (joint between the leaf and stem). Flower buds are red or purple-hued and open to reveal white, four-petaled, fragrant blooms. From these come highly variable, large, fragrant fruit that are round to pear-shaped and generally yellow. They have thick leathery skin dotted with oil glands and juicy, variously tinted, acid flesh with or without many seeds. Fruits ripen in the late fall through winter and are harvested by hand as they mature.
The cultivar ‘Oroblanco’ is a patented cultivar developed by the University of California. The trees are exceptionally vigorous and have a spreading form. Smooth-skinned, yellow-green fruit ripens early to mid season. The fruit is medium to large-sized, round and flattened at the poles with a large hollow center. The flesh separates into sections easily, is very pale-yellow to white, seedless, juicy, and has a mild flavor.
Like most citrus, they are cold sensitive and prefer locations with warm, dry winters, and cool summers. If fact, trees can only tolerate a few degrees below freezing for a few hours. Grapefruits require full sun and are tolerant of most soils, even poor soils, with ample drainage. Though moderately drought tolerant once established, they must have regular applications of water for good fruit production.
Grapefruit trees have large rounded canopies and require plenty of space, more than orange trees, for good growth. They are heavy feeders needing regular applications of fertilizer. There are a multitude of varieties available, some ideal for commercial production and others best suited to backyard orchards. Most are grafted on to rootstocks, which impart tolerances to local soil, pest and climate conditions as well as preserving the desired varietal characteristics.
Though large, these trees can be trained to be more compact via grafting and pruning. Those on dwarfing rootstocks make great tub or conservatory specimens. No backyard orchard in subtropical and tropical zones is complete without at least one prolific and long-lived grapefruit tree.