The importance of curing onions before storing them became painfully obvious to me a few years ago as I watched my hefty crop of yellow globes, carefully braided to lend my kitchen the "gourmet" look I fancied, slowly turn green, then gray and finally black as the mold grew and spread. The only onions I was able to enjoy that year were the ones I used in the first two weeks after harvesting.
I had blithely assumed that airing them out was much the same as curing them. Not so. The curing process removes excess moisture from the flesh of onions so that they don't rot when stored together. Curing is also extremely important for the proper storage of vitamin-rich sweet potatoes. I have, however, ignored curing advice on hard-shelled winter squashes and have never been daunted by the results.
For those clever gardeners who gained a jump on the season by planting onion sets last fall, the time for harvesting is fast approaching. When the stalks are yellowing and falling over, the onions have finished growing. They should be pulled gently or forked out of the ground to prevent the stalks' breaking off. Lay them out in the sun to dry for three or four days, ideally on top of a couple of old screens set up on two-by- fours or bricks, which will allow air to circulate. Barring that, a table or wide board will do, but you'll have to turn the onions once or twice. They should be laid out so that they aren't touching during the curing. If rain threatens, cover them or move them under shelter. The important thing is that they stay in the sun for at least three days.
As you harvest your onions, you'll note that some have thick, green stalks. These won't keep as long as onions that are harvested with thin, yellowing stalks. Use the green ones first, after curing.
If you want to braid onions, do it as soon as the curing's done. If you wait too long, the stalks will become brittle and break when you try to braid them. If you don't braid them, cut the stalks to about an inch and store the onions in the same kind of orange plastic nets you see in the supermarket. Or store them in metal baskets or cloth "files," those handy French string shopping bags available fairly cheaply from kitchen specialty stores. I wouldn't advise storing them in a good woven basket -- not because it'll hurt the onions, but because baskets shouldn't be used for storing any sort of fruit or vegetable -- something may rot and damage the basket. SPACE AVAILABLE: With onions harvested and pea vines pulled, you'll have extra space in the garden for new crops. While it's too late for a lot of long-growing vegetables and too early for fall crops, don't let the newly found space lie fallow. It's too easy to rationalize that in a month you'll be ready to plant fall-bearing peas and in two months fall onion sets will go in. Other areas in the garden will also open up in the next few weeks as you pull whole rows of beets, beans, corn and so on. Plant pumpkins, cantaloupe or even pickling cucumbers where the peas were. Vining squashes will welcome a fence to climb. Sow a handful of brassicas -- broccoli, cabbage, Brussels sprouts, cauliflower -- where you've pulled the onions. In six weeks you'll need to transplant brassica seedlings to ensure that they thrive, and the space will again be free for something else. If you want to put fall peas and onions back in the same beds from which you just pulled them (the excellent practice of rotating crops is much more important in year-to-year garden planning rather than inter- seasonal), plant some quick-maturing vegetables -- radishes, lettuce or beets, which are delicious when harvested small and sweet. Areas that have yielded one crop and are free for a second need very little preparation -- one of the big advantages to using the soil again quickly. Pull all weeds, dig in a little compost if the soil needs replenishing (adding nutrients isn't really necessary if the soil is already quite fertile) and water the area down well. A light mulch will keep that moisture in, and the bed or row is ready to receive new seeds or seedlings.