Grapefruit trees (Citrus x paradisi) are relatively new to the United States. Brought to Florida at the beginning of the 19th century, the nutritious fruit quickly gained in popularity. As of 2011, the United States produces the majority of the world's commercially sold grapefruit. Trees vary in their rate of growth depending on their origin. How fast the grapefruit itself grows and ripens varies, but on average it takes around nine months.
Grapefruit trees can grow to maximum heights of between 20 and 50 feet. With their impressive sizes, evergreen leaves and huge, fragrant white flowers, they make quite an attractive display. Height does not equal maturity, however. The trees are considered mature when they start to produce flowers and fruit. The time it takes for them to reach this point varies. In general, seedlings may not fruit until five or more years after they've been planted. Grafted trees on rootstock will bloom more quickly; as soon as two years after planting.
Grapefruit does not ripen after it has been harvested. For that reason, the fruit must remain on the tree until it is fully mature. This can take as little as seven or as long as 11 months. Grapefruit is tropical, and as such, the fruit is usually harvested during the milder winter months of December and January. Legally, grapefruit can be harvested as early as September according to Florida law, but it first must be sprayed with lead arsenate, which reduces the acidity of the fruit. The longer the grapefruit remains on the tree, however, the larger and more commercially valuable it becomes.
Several factors can affect the growth time of both the trees and fruits. Late freezes in fall and winter right before harvest time can destroy the fruit before it can be harvested. It's not just freezes that can hurt the trees. Temperatures that are only just slightly cooler than normal can slow or halt growth. Grapefruit trees are not disease hardy, either. Even healthy trees are susceptible to viruses and canker diseases, but trees that have been weakened by cold winds and drought conditions are much more likely to succumb and fail to grow.
"Duncan" was the first ever commercially grown grapefruit tree. Desirable for its cold hardiness, it also produced fruit with a lot of seeds. For that reason, it is not commonly grown today in the United States. "Marsh" is a seedless or low-seed variety desirable for its juicy, rich flavor and ability to store well. It is the leading cultivar grown around the world. "Redblush" began as a mutation of "Thompson" but is now one of the top cultivars grown in the United States. It is also known as "Ruby Red" and is notable for its red flesh.