My onions don't store well. Why?
The storage life of onions is largely determined by the variety (cultivar), harvesting and drying procedures, and storage conditions.
When selecting onions, choose varieties that store well, such as ‘Copra,’ ‘Stuttgarter,’ and ‘Sweet Sandwich.’ ‘Walla Walla,’ ‘White Bermuda,’ and ‘Yellow Sweet Spanish’ are poor keepers.
Harvest onions when most of their tops have fallen over and begun to dry. After harvest, dry or cure the onions in a warm, dry, well-ventilated location for 2 or 3 weeks. When the onions tops are dry, cut off the tops 1 inch above the bulbs.
Place the cured onions in mesh bags, crates, or wire baskets and store in a cool (32 to 40 degree Fahrenheit), dry location. Onions will sprout if storage temperatures are too warm. The bulbs may rot in damp locations.
‘Copra,’ ‘Sweet Sandwich,’ and other good keepers can be stored for several months if they are properly harvested, dried, and stored.