When flowering has finished Tuberous begonias can be lifted and stored away until their next growing season, usually in September.
In March apply potash fertilizer, this will help mature and harden the tuber.
Stop watering your Begonias in April. Withholding water enables the plant to die down naturally as food value is returning to the tuber for storage. Remove the flowers but don’t remove the foliage. Allow the foliage to turn yellow and fall off. Allow the stem to come off naturally.
Around June/July when the potting mix has dried completely, lift the tube. Try not to break the larger roots. Leave the tuber to sit for more drying of the old mix to occur, from the roots. When this has dried completely, brush off the dried soil carefully so as not to damage the non dried roots.
Before storing your tuber, dip in 10% Demestos or 5% Janola solution or in straight Methylated spirits and dry. Dipping well help minimise storage rot. Store in a cool, dark place. Wrap in paper or store in sand or sawdust. Check your tuber regularly. If the tuber develops a wrinkled skin the spray with a little water. Remove the old stem scab with your finger nail. Be careful not to damage the tuber.