thiemcathe. That is generally true, particularly dealing with houseplants. My rule of thumb is to increase the pot diameter 2" when repotting. Orchids are different though. I might increase the pot size only 3/4"-1". Plants that are normally outside (full-sun plants) are also different. Does one limit their root growth when grown in the soil, outside? The main things to remember is to have the potting soil really well-draining, have plenty of bottom holes or at least one large one, empty the catch-saucer after watering, and allow the top two or so inches of potting media to dry out before re-watering. Within reason, I really don't think you can over-pot a citrus tree if you follow those simple rules.