The peak of ripeness for dragon fruit is about 30 to 50 days after flowering. As it ripens, the red variety turns from green to red; pick it about four days after the color changes. If it's too blotchy, it's probably overripe; if it's too firm, it's not ready. Dragon fruit, unlike bananas, do not continue ripening after being picked, but they're sweeter a few days after picking.
You can eat dragon fruit fresh, though it's better to let it sit a few days. Just cut it in half and enjoy, or use it in a salad or as preserves. You can refrigerate dragon fruit -- it's even better chilled -- and you can sprinkle it with lemon juice. Dragon fruit keeps for about two weeks -- if cool enough. Both the seeds and flesh are edible.
Since dragon fruit is a climber, it usually needs support. The red dragon fruit is not self-fertile, but the white one is. The plants can fruit most of the year, if conditions are right. There also is a yellow dragon fruit, but it's Selenicereus megalanthus, a different genus.