Vine-ripened tomato by John Spottiswood.

For best flavor, tomatoes should stay on the vine until they're fully ripened. This is a tall order for growers, who prefer to pick tomatoes while they're still green and sturdy, and then gas them with ethylene until they turn red. Vine tomatoes, on the other hand, are picked after they begin to "break" or turn red, which allows them to develop fuller flavor. Expect to pay more for the special handling required to bring these to market.