Storing Tubers for the Winter
The ideal temperature for storage of tubers is between 4°C and 10°C (40-50°F), in a dry, airy place that is not conducive to mold. The tubers cannot tolerate frost, so they must always stay in "above zero" conditions. A heated garage is often idel, whereas a basement may be too humid.
Tubers are best stored in cardboard or wood boxes - compared to plastic ones, these offer you some air circulation. There are also different materials you can use to insulate/wrap the tubers inside their container:
Horticultural vermiculite (coarse grain) can absorb excess moisture without drying the tuber and allows air circulation in the container. This product is expensive and it is best to wear a mask when handling it. Please avoid "construction" vermiculite as it is much finer and dustier, and your tubers will be less protected against rot.
Peat moss is another product which can work well while keeping costs down. Be vigilant with regards to moisture, the bag may have been pierced. Also, if it is a little moist, you can add a dry product to offset.
Wood chips (wood shavings) are the least expensive solution, but moisture and humidity are again a threat. A punctured bag may have altered the humidity level as well. Wood chips are great at absorbing excess moisture, but too much dust can reduce air flow and promote rot on your tubers. Also, wood chips can be bought just about everywhere.
Some people use sand, which can also be abundant - depending on where you may live. Sand is rather heavy to work with and can sometimes promote the tuber to germinate a little early in the season.
Having choosen your product, insulate the bottom of the box with a good layer. Lay a row of tubers and cover again with your product. Depending on the box's height, you may add more rows.
There is even another method using Saran Wrap!
Is a large tuber better than a smaller one?
The size of a tuber will not never be indicative of the plant's height or size. What to look for is the tuber's overall strength and consistency, and especially that there is no break in the narrow section between the tuber and buds (the collar). A break will prevent the transfer of energy accumulated in the tuber to the buds.