If you’ve ever grown onions, you know the harvest is one of the most rewarding moments of the season. But the real magic comes afterward: when you cure, store, and preserve them properly, your onions can last for months and provide homegrown flavour all winter long.
In this guide, I’ll walk you through exactly how to tell when onions are ready to harvest, the critical steps for curing them, the best ways to store them so they last, and different methods to preserve your harvest for long-term use.
How to Tell When Onions Are Ready to Harvest
Wondering when to harvest onions? The main sign is simple and you can’t miss it: when the green tops naturally flop over at the neck and start to dry out, the bulb has stopped growing and is ready to pull.
Tips for Harvesting Onions:
- Wait for the Flop: Be patient and wait until at least half to three-quarters of the tops have fallen over before harvesting the whole crop.
- Pick a Dry Day: If you can, harvest on a dry, sunny day. Pulling onions from dry soil helps the curing process start off right.
- Harvest Gently: Gently lift the bulbs with your hands or a garden fork. Be careful to avoid bruising or damaging the bulbs, since nicks and cuts will shorten their storage life.
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How to Cure Onions for Long-Term Storage
Curing is the most important step if you want your onions to keep for months. This process dries out the outer layers and the neck of the onion, creating a protective papery skin that seals out moisture and prevents rot. Without proper curing, they’ll spoil quickly.
Here’s how to cure onions step-by-step:
- Lay Them Out: Lay the onions in a single layer in a warm, dry, and well-ventilated spot. A greenhouse, a dry shed, a covered porch, or even a garage all work well.
- Keep Them Out of Direct Sun: While they need warmth, direct, intense sunlight can cause the bulbs to get sunscald, which creates soft spots.
- Be Patient: Let them cure for 2–3 weeks. You’ll know they’re ready when the outer skins are dry and papery, the neck is completely dry and tight, and the roots are withered.
- Prep for Storage: Once fully cured, you can prepare them for storage. Use scissors to trim the dried tops down to about an inch, and trim the roots off the bottom. Brush off any loose dirt.
Best Storage Conditions for Onions
For long-term storage, onions need three things: cool temperatures, low humidity, and good air circulation.
- Temperature: 32–40°F (0–4°C) is the ideal range. A cool basement, a root cellar, or an unheated (but not freezing) garage are perfect.
- Humidity: Low humidity is key to preventing mould and rot.
- Containers: Use mesh bags, wire baskets, or even old pantyhose—anything that allows air to move freely around the bulbs. Don’t pack them in plastic bags or sealed containers.
⚠️ Don’t Store Onions with Potatoes!
This is a classic root cellar mistake. Potatoes release moisture and ethylene gas that can cause onions to sprout and spoil much faster. At the same time, onions release compounds that can encourage potatoes to rot. Keeping them stored separately will extend the shelf life of both crops.
Remember, sweet onion varieties (like Walla Walla) have a higher water content and don’t store as long as pungent storage onions (like yellow or red onions). Plan to use your sweet onions first.
How to Preserve Onions for Long-Term Use
Even well-cured onions won’t last forever. Preserving onions ensures you have them ready in your pantry all year round, and it’s a great way to use up any bulbs that have soft spots or thick necks that won’t store well. Here are some of the best methods:
1. Freeze-Drying Onions
This is one of my favorite methods. Freeze-dried onions are lightweight, incredibly long-lasting, and rehydrate beautifully for use in soups, stews, and casseroles. Just chop them, spread them on the trays, and let the machine do the work.
2. Freezing Onions
Freezing is the quickest and easiest way to preserve onions. Simply chop or slice your onions, spread them on a tray to freeze individually for an hour, then transfer them to freezer bags or containers. This way, they won’t clump together, and you can easily scoop out just what you need for a recipe.
3. Dehydrating Onions
Dehydrated onions are a pantry powerhouse. Slice or dice your onions, dehydrate them at a low temperature until they are brittle and crisp, and store them in airtight jars. You can grind them into your own onion powder or use the dried pieces in seasonings, soups, and broths.
4. Canning Onions (French Onion Soup)
One of my favourite ways to can onions is by making a big batch of rich, delicious French Onion Soup. It’s shelf-stable and perfect for:
- A quick and comforting weeknight soup.
- Pouring over beef roasts before cooking.
- Making a rich, flavorful gravy.
Final Thoughts
Knowing how to properly harvest, cure, store, and preserve onions means you can stretch your harvest for months to come. Whether you’re filling mesh bags for the root cellar, freeze-drying them for convenience, or canning jars of soup for easy winter meals, onions are a pantry staple that is well worth the effort.