Tangerines are among the most cold tolerant of all the citrus plants. Tangerines become ripe faster than other citrus fruits like grapefruits or oranges, which allows them to grow in colder climates. The timing of a tangerine harvest will vary depending on the specific variety being grown and where the growing takes place. The majority of tangerine plants will be ripe sometime during the winter or at least by the first few weeks of spring. Tangerines signal their ripeness by becoming more soft and developing a rich orange hue. Once plucked from the branch, a tangerine will have a shelf life of roughly two weeks.