The Rio Red grapefruit was developed in Texas and grows throughout that state today. The tree is suitable for growing in hardiness zones 9 and 10 and features fragrant white blossoms and deep red fleshed fruit. Grapefruit trees got their name from the fruit's habit of growing on grape-like clusters. They are the only citrus fruit to originate in the West Indies and not southeast Asia, and are believed to be an orange-pumelo hybrid.
The Rio Red grapefruit developed as a natural mutation from irradiated budwood of Ruby Red seedlings in 1976, as Texas A&M notes. Texas A&M scientists released this variety for commercial production in 1984.
Rio Red grapefruit has a buttercup-yellow rind with pink blotches. The fruit develops a weighted ovoid shape called sheepnose, looking fatter at the bottom and lighter at the top. The fruit is deep pink or red in color, nearly as bright as the Star Ruby variety.
Rio Red, like all grapefruit varieties, should bear fruit the third year after planting, notes Texas A&M. To help the tree grow properly, gardeners should remove any fruit that develops in the first two seasons, so the tree can direct its energy into growth rather than fruiting. In a first year of fruiting, a Rio Red grapefruit tree might produce 25 lbs. of fruit, increasing to as much as 250 lbs. by its 10th year of production.
Most Rio Red grapefruit trees average 15-20 feet in height. The tree branches bear small thorns. Grapefruit tree leaves are dark green and ovoid, reaching 3-6 inches in length. The easiest way to distinguish a Rio Red grapefruit tree from other grapefruit trees is via the fruit's rind. Rio Red grapefruits maintain a red blush throughout the season, unlike other grapefruits that lose their red hue.
In Texas, grapefruits grow predominantly in the Rio Grande valley, though growers can plant them in other parts of the state. Initial grapefruit trees planted in the state bore white fruit; pink or red grapefruit developed through natural mutations and plant breeding. Today, Texas grows predominantly red grapefruit varieties, among them the Rio Red.