Answer: It is interesting that plants generally have a root system that is in proportion to the top portion of the plant. If you trim off roots, you would need to trim off top growth to maintain that balance. With larger plants such as citrus trees grown in the same size (large) tubs for many years, root pruning is done periodically as well as continuing branch pruning to keep the plant at a certain limited size. In general, when repotting, it is best to keep all of the roots. Move up just one pot size and try to match the potting mix to the original type. If your plant is getting too big, you may be able to divide it and limit size that way. Whether or not a plant can be divided successfully depends on which specific plant it is. Division is sometimes done by gently pulling the plant apart into sections of root with corresponding top growth, or it is cut using a sharp knife, or in some cases with very woody plants a saw is used. I hope this helps.
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