Grapefruits are harvested for several months.
image by Andrey Volodov/sxc.hu
Grapefruits are actually a natural hybrid of oranges and pummelos. They are one of the largest citrus fruits and have a bitter taste. Grapefruit trees are grown in all-year warm climates, like Florida and southern California and can grow up to 45 feet tall, making harvest a bit more challenging, but possible.
Harvest grapefruit beginning in September or October only if you sprayed your tree with lead arsenate after blooming. If not, they will be ready for harvest in a couple months, however keep an eye on your tree for large and firm grapefruits.
Spot-pick your grapefruits when they are large and firm. You can do this until May. However, the sooner you pick them, the less they will affect next year's fruits, which may be minimal if you picked a lot of your grapefruits late in the season.
Hand pick the grapefruits on the lower branches and use a ladder to climb up higher in the tree to pick fruits up high. You can also use a hook, but you may inadvertently damage the fruit using this method.