Answer: In cold winter areas citrus trees can be grown indoors from September through April and then taken outdoors a placed in a sunny spot. Indoors, citrus trees need average warmth, freedom from drafts, ample water, and well draining soil. You may need to supplement natural light with fluorescent or gro-lites especially made for plants. Turn the light on for 12-14 hours each day and turn it off at night. Citrus trees need ample moisture, so water often enough to keep the soil moist but not soggy, and feed in the spring and summer months with a diluted liquid fertilizer, especially if the leaves are yellowish instead of glossy deep green. Watch out for scale, aphids and mites, and use insecticidal soap or light horticultural oil according to label instructions if they do show up.
Transplant your tree into the next larger sized pot in a few years. (I look for roots growing through the bottom drainage holes, which indicates they need more room, and then I repot.)
Be sure to give your tree a gradual transition from indoors to outdoors, and vice versa, so it has time to adjust to the changes in the environment.
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