Citrus trees are tropical plants that require lots of light, warmth, and adequate moisture in order to thrive and produce fruit.Though it varies by variety, citrus trees tend to bloom in spring, with fruit developing over the summer, and ripening slowly into the fall and through the winter. Although they are self-fertile, when grown outdoors, citrus trees will be pollinated by insects or wind. It's a good idea to hand pollinate your plants. Though they can still survive in lower light conditions, they will be unlikely to flower or produce fruit. When the weather warms up, you can move plants outdoors during the growing season to give them access to natural light. Bring them outside once the air temperatures are consistently above 50F, transitioning them to their new conditions over a period of a couple of weeks. Gradually move them from a partly shaded spot to one with full sun, eventually setting them in the sunniest spot you can find. Provide protection from wind, and keep the pots in their saucers to maintain good drainage.