Answer: In the fall, dig them up as soon as frost kills the stems. Do not pierce them with your shovel or fork when you dig them up -- work carefully and remember they will be much bigger now than they were last spring. Cut off the stems and discard. Wash off the soil, air dry at room temperature for a few days, then store. Pack them in a cardboard box or paper bag with shavings or dry peat moss or vermiculite or wadds of newspaper, but do not allow them to touch each other. Store them at about 50 degrees.
Check them periodically and remove any that show signs of rotting. If they rot, it is usually because they were damaged during digging or they are too cold or they were stored too wet. If they start to shrivel, they are too warm. Sprinkle with just a little water to rehydrate and move them to a better place. Sometimes it takes a little trial and error to find the right place to keep them. Some gardeners are lucky and just dig them up, toss them clinging dirt and all into a box and shove it in a back corner of their drafty old basement -- keep in mind modern homes often have basements that are too warm.
In the spring, pot them up using clean pots, freshly dampened soilless potting mix, and pot them just barely covered. Water to dampen and settle the soil at planting, but water sparingly after that until they are actively growing. They need warm soil to grow, and once they sprout they need as much sun as they can get. Do not start them too early because you can't plant them outside until the soil has warmed up anyway -- say two weeks after the last frost or so. If you keep them as container plants you can move your containers outside to a sheltered spot on sunny days and bring them in at night. If you can keep them above 50 degrees that is best.
I hope this helps!
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