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Growing Grapefruit: Citrus paradisi

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Overview
A member of the Rue family. Modern citrus fruits, according to genetic analysis, are complex hybrids arising from mandarin, pummelo, citron and pepeda ancestors, refined by more than four thousand years of cultivation. The grapefruit was first identified in Barbados, resulting from an accidental cross between Sweet Orange and Pummelo. Many cultivars and hybrids of grapefruit with other citrus are now available.

Description
Form: Tree.
Lifespan: 35-50 productive years.
Leaf retention: Evergreen.
Growth rate: Moderate.
Mature Size: 15-20' high and as wide.
Flowers: White, four petals, fragrant.
Bloom: Winter.
Self-fruitful: Yes, although hand pollination may be necessary if bees do not arrive in sufficient numbers.
Years before fruiting: 3 for grafted trees, 10 for those grown from seed.
Fruit: Round to oval, thick yellow rind, flesh can be slightly bitter, white, pink or red, aromatic. The red fleshed cultivars tend to be sweeter.
Months for fruit to ripen: 10.
Storage after harvest:
Leaves: Glossy dark green, lance-shaped, smooth margins.
Stems: Short thorns on twigs. Bark is prone to sunscald if not shaded by leaves, especially in higher temperatures.
Roots: Usually grafted onto a special rootstock that is pest resistant and adapted to the local climate.
Cultivars of Note:
'Rio Red' - Sweet red flesh, few seeds.
'Oro Blanco' - Sweet yellow flesh, few seeds, easy to peel, a hybrid of grapefruit and pummelo.
Wildlife: Attracts bees, butterflies, birds, mammals, including those which climb the tree to pick the fruit.
Toxic / Danger: Possible thorns. Grapefruit can interact with many medications, including chemotherapy, making them more, or less, effective and throwing off the prescribed dose.
Origin: A natural hybrid first recognized in Barbados.

Cultivation and Uses
USDA hardiness zones: 9-11. Somewhat less cold-hardy than oranges.
Sunset climate zones: 8-9, 12-24.
Chill hours: None.
Heat tolerant: Yes.
Sun: Full sun.
Drought tolerant: Depends on rootstock. Drought will damage fruit crop.
Water after becoming established: Every two weeks, to weekly when fruiting in the hottest parts of the summer. Roots can extend twice as far as the canopy, so water beyond the canopy. Young trees need watering more often than older trees even though older trees consume more water.
Soil: Well drained, can be mixed with aged compost and sand, pH 5.6-8.5 (acidic to alkaline).
Fertilize: Apply a citrus fertilizer mid-February, May, and early October. Follow directions on package. Or, if using organic fertilizer, apply every month from mid-February to early October. Do not fertilize after October to keep the plant from producing new growth that will be harmed by early frost.
Mulch: Keep all mulches at least 1' away from the base of the trunk. Keep grasses and vegetation 3' away from bud union on trunk.
Planting: Place the root ball so that it is slightly higher than the surrounding soil and not at the bottom of a large basin that will cause overly wet soil during rains and subsequent root rot.
Prune: Remove sprouts growing on the trunk under the bud union as they occur. Remove dead, damaged, crossing and weak branches in late winter. When shaping into a tree, unshaded trunks and branches should be painted with a white tree trunk paint to protect against sunscald.
Litter: Dropped fruit must be picked up immediately to avoid attracting wild animals.
Propagation: Cuttings grafted onto disease resistant rootstock adapted to the local climate. Trees grown from seed are usually true to their parent tree characteristics.
Uses: Ornamental, edible fruit.

Comments
The fruit and flowers pictured are 'Oro Blanco'.



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