Protect under glass or in a frost-free, sheltered location until risk of frost has passed, then plant out or pot up into larger containers. While in growth, provide a high-nitrogen liquid feed each week in June, then a high-potash fertiliser each week from July to September. In mild areas, leave them in situ over winter, but protect the crown with a generous layer of dry mulch. In colder areas, carefully lift and clean the tubers once the first frosts have blackened the foliage and allow them to dry naturally indoors. Then place the dry tubers in a shallow tray, just covered with slightly moist potting compost, sand or vermiculite and store in a frost-free place until planting out again.