There’s not a whole lot to say about prepping onions for storage, except that the goal is to dry them sufficiently before placing them in storage.
We have a table on a porch where we gather some small amounts of vegetables as they are harvested. A spot in a garage or even the shade of a tree would work as well, as long as the food items are protected from getting rained on.
We lay out a few pieces of newspaper to make the clean up go a little faster. The newspaper will catch dirt and shed pieces of the outer wrapping of the onions.
Use a thumb and fingers to remove clumps of dirt and long roots as well as wet outer layers of the onion skins.
Lay the onions out on the newspaper so that the bulbs are on their sides and the root section is exposed to the air. We want the onion to dry out well before cleaning off all the dirt and outer layers of the bulb.
Make sure the onions are not touching each other and that they have some room for air circulation for the best drying.
Pick an area where the onions can be laid out to dry for a couple of weeks. When harvesting the onions on a sunny day, this drying time might be reduced as the onions will dry nicely in the sun. However, the tops may still feel “green” for a few weeks.
Use any of the damaged onions in the kitchen first and also use first the ones that retain the least outer skins as they won’t store as well as those onions that are completely wrapped by their own skins.