Answer: Begonia tubers increase in size each year and after three years or so, the flower display will begin to deteriorate. It's best to divide the tubers in the early spring, after the buds have begun to swell. Use a sharp knife and divide into as many pieces as you like, as long as each piece has at least one bud on it. But remember, the smaller the piece, the less food reserves it has and the longer it will take to reach flowering size. The cut edges will be prone to fungus attacks, so leave the tubers on a flat surface for a few hours to dry, or dust them with a fungicide. Then pot up each section, making sure the cut edges are buried, but the shoots are above the soil level.
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