Derived from the Ruby grapefruit, Rio Red is the predominant variety of grapefruit grown in the South and is suitable for growing in subtropical areas. The Rio Red displays pink fruit that does not lose its color throughout the season, unlike other red or pink grapefruits. Young grapefruit trees need sufficient nurturing, protection from cold and watering to survive. Even mature trees need regular care to stay healthy.
Plant Rio Red grapefruit trees in a sunny, preferably south-facing location. This provides protection and shelter from cold and wind. Avoid planting the tree too close to buildings or walkways so the mature tree has enough room to grow.
Build a watering ring around the base of the newly planted tree by creating a moat in the soil. Fill the ring with water to keep it moist. Water newly planted trees two to three times during the first week and once or twice a week for the next few weeks. Gradually decrease watering until you're watering every seven to 10 days.
Mulch the soil around the base of the tree in a 2- or 3-foot ring. This helps keep the soil temperature warm and keep moisture in.
Wait to fertilize the newly planted Rio Red grapefruit until it begins to grow. Once you see new growth, fertilize monthly until October. Scatter the fertilizer around the tree's trunk and water the tree to disperse the fertilizer. During the first year, apply 1/2 cup of 12 percent to 21 percent nitrogen fertilizer or 1 cup of 8 percent to 13 percent nitrogen fertilizer. In the second year, double those amounts, then double again in the third year.
Provide winter protection to the grapefruit tree if you live in an area prone to frost by stringing the tree's branches with lit Christmas lights. Wrap the entire tree in burlap, from the trunk to the branches. Secure the burlap with safety pins. Leave the tree wrapped until the low temperature warms to above 40 degrees Fahrenheit. Alternately, bury the tree's trunk in a soil bank so only the branches are above ground.
Prune any dead or damaged wood annually. Grapefruit trees require little pruning, but dead and damaged wood must be removed for the overall health of the tree. Prune in the late winter after you've harvested the grapefruit.