How do you keep onions from rotting?

QUESTION: I’m growing onions and several onion alternatives in my garden. I’ll harvest more than I can cure and use. How do you keep onions from rotting? – Tim S

ANSWER: As onions are one of the most often used kitchen ingredients, it is unfortunate that they tend to go soft or start sprouting before you get around to cooking with them. It is in the best interest of anyone who cooks to learn how to best store onions to keep them from rotting.

General Onion Storage Tips

Keep onions in a cool, dark, dry, well-ventilated room. Keep out of humidity, preferably in temperatures around 40-50 degrees F. Keep out of plastic bags and other enclosures that inhibit ventilation, instead gather them together in a mesh or netted bag, an open basket, or even pantyhose to ensure that they get plenty of fresh air. Darkness is also important, as the absence of sunlight reduces humidity and temperature fluctuations.

Whole Onions – Avoid storing whole onions in the refrigerator. Store bought onions have papery skin, as they have been cured to reduce moisture and to help them last longer in storage. Putting whole onions into the fridge exposes them to cold, humid conditions, which can cause them to get mushy or spoil faster than usual. This rule does not apply to peeled, sliced, or diced onions, which should be stored in the fridge to keep them fresh for about seven to ten days after they have been cut. To keep cut onions longer than seven to ten days, store them in freezer bags in your freezer.

Peeled Onions – Once an onion has been peeled, it needs to be kept in an airtight container in a refrigerator set to 40 degrees F (or below) to protect against bacterial contamination. Peeled onions correctly stored in the fridge will last 10-14 days, according to the USDA.

Sliced, Cut, or Diced Onions – Cut onions can last in the fridge for up to 10 days. Wrap tightly in plastic or keep in a resealable bag. For longer storage needs, place cut onions in the freezer in a freezer bag to store for three to six months. 

Cooked Onions – Cooked onions can be stored in the fridge for three to five days. Place them in an airtight container or resealable bag within a few short hours from cooking. For longer storage needs, keep cooked onions in the freezer for up to three months.

Pickled Onions – Pickled onions that are prepared and stored properly will last up to six months. Place in a glass or ceramic jar with vinegar and a mix of your choice of salt, sugar, and spices. Once the jar has been opened, keep it in the fridge to help them last.

Shallots – Like onions, shallots store best in a cool, dark, dry, well-ventilated room. Store in a mesh bag, bamboo steamer, open basket or pantyhose for optimal ventilation. Properly stored shallots should stay fresh for up to 30 days. For longer storage needs, keep in the freezer to preserve for up to six months. 

Spring Onions & Leeks – Spring onions and leeks share many characteristics and are also stored in a similar way. If you are planning to use your onions or leeks within one to two days, just leave them sitting on your counter in a jar with some water. Just be sure that it’s not too hot or humid in your kitchen, or they may be prone to wilting. If you don’t plan on using them within one or two days, wrap them up in a damp paper towel and secure the stems with a rubber band. After wrapping and securing them, place them in the crisper drawer of your fridge where they will keep for up to one and a half weeks. For longer storage needs, chop, place in a freezer bag or airtight container and freeze your spring onions and leeks

Onion Shopping Tips

If you don’t growing onions, make sure you know how to select onions. Choosing which onions to purchase may be equally important to knowing how to store them correctly. For white, red, and yellow onions, pick out ones with dry, papery skin. The outer layer should also be free of any signs of moisture or spotting. Select onions that are firm and heavy for their size, which will prove that they are juicy and not too ripe.

Be sure not to pick onions that have begun to sprout, as they will rot very quickly. Before tossing your picks into your grocery cart, give them a quick smell. If they have an unpleasant odor, it could mean that they are too ripe, or bruised. When selecting spring onions, go for ones that are bright white with firm stalks and bulbs with no spots or blemishes. Avoid selecting spring onions that are wilting or have a slimy film on them. When picking out leeks, look for ones with lots of white and green. Pick out leeks with crisp, firm stalks, that are free of spots or discoloration.