Grapefruit trees (Citrus paradisi) are common throughout the subtropical and tropical regions of the United States. They grow best in these zones. Grapefruit is a cross between a sweet orange (Citrus sinensis) and a pommelo (Citrus maxima). It did not become popular in the states until the early 1800s. Grapefruit trees are relatively hardy outdoor trees, when grown in zones 9 and 10. Cooler regions need to grow the tree in a container, as grapefruits are cold sensitive. Provided with the needed growing conditions, a grapefruit tree is not that difficult to grow.
Select an area to plant your grapefruit, which receives full sunlight. The tree should receive, at a minimum, five hours of sunlight each day. Grapefruit trees will eventually die if grown in the shade.
Consider the size of a mature grapefruit tree when selecting the site. Grapefruit trees can reach a height of 20 feet and have a width of approximately 15 feet. Do not plant the tree where it will interfere with your house or power lines.
Eliminate any unwanted grass or weeds growing in the planting site. Keep an area that is at least 3 feet in diameter free of vegetation at all times. Do not place mulch around the base of the tree. This can cause the grapefruit to develop root rot.
Amend the soil with sand, if the soil is thick and does not drain well. There is no need to amend the soil with compost if you are planting the tree in sand. Grapefruit trees prefer to grow in soil that is loose and drains well. They will not live in flooded conditions.
Add lime to the planting site if your soil is too alkaline. Mix the lime into the existing soil. If the tree is already planted, spread the lime underneath the canopy and water it well.
Water a newly planted grapefruit tree twice a week for the first four weeks. Give the tree a deep watering once per week, once it has established itself. Grapefruit trees produce more blossoms and fruit if watered on a regular basis.
Fertilize the grapefruit tree with a high-quality citrus fertilizer three times per year. Apply the fertilizer in early spring, summer and fall. Fertilizing the grapefruit on a regular basis will give you a better harvest.
Protect grapefruit trees from frosts and freezes. They will not tolerate freezing temperatures for too long. Place a blanket over the tree and place a 60-watt outdoor lamp underneath the cover. You can also hang Christmas lights off the tree to keep it warm. Water the tree deeply the day before freezing temperatures are expected. This will keep the roots warmer. Bring a container-grown tree inside.
Prune off only dead wood from the tree, or branches growing right above the graft. If the tree was damaged in a freeze, wait until late spring before you prune off any branches that look dead. Sometimes a branch will look dead only to sprout back to life, months later.