When to Harvest Onions So You Can Cure and Store Them for Months

If you spend just one minute browsing savory recipes, you’re bound to run across a recipe that calls for onions. From burger toppings in the summer to cozy French onion soup in the fall, onions are useful year-round. Fortunately, they are easy to grow in your garden.

To properly store your onions after harvesting them, start by selecting suitable storage varieties. Next, you’ll need to harvest your onions at the right time, cure them, and store them in optimal conditions. Follow this guide to make sure your onion harvest lasts for months in your pantry.

Best Onion Varieties for Storage

Properly stored, onions can last for months. The best storage onion varieties have a high sulfur content—they’ll make you cry—and a strong flavor. Mild-flavored or sweet onion varieties will likely only keep for a few weeks. Good storage options include ‘Stuttgarter’, ‘Yellow Globe’, ‘Copra’, ‘Patterson’, ‘Redwing’, and ‘Ebenezer’ onions. Most of these (except for ‘Redwing’ and ‘Ebenezer’) are yellow varieties and hardy in zones 3-9. Check with your local cooperative extension office to determine which types will grow best in your area.

When to Harvest Onions

A good rule of thumb for when to harvest onions is to wait until half the leaves have died back. As onions approach maturity, “they start accumulating water and sugars in the bulbs and pulling sugars and nutrients from the leaves into the bulbs, which causes the leaves to die back and the tops to flop over,” says Genevieve Higgins, Extension Vegetable Production Educator at the University of Massachusetts. But Higgins cautions, “Don’t wait until the foliage on every plant has fallen, or you run the risk of the plants that matured earlier becoming over-mature.”

Use a garden fork to loosen the soil around your plants, taking care not to skewer the onions. Then lift your onion bulbs out of the ground and brush off the excess dirt. If the soil is loose already, you can simply pull them up by hand. Don’t remove the leaves. “It’s best to leave the tops on onions until they are fully cured. Cutting off the tops before the neck is cured down provides an entry point for bacteria and fungi, which can lead to bulb rots,” says Higgins. Any onions that have flowers should be used as soon as possible; they won’t store well.

Curing Onions

Proper curing is critical for onion storage. The outer layers of the bulb need to dry sufficiently to protect the interior portion of the bulb from rot and mildew. They can be cured outside in dry weather by laying them on top of the soil or on a clean, dry surface. Don’t wash them; just brush off loose dirt.

“Be careful not to leave onions out in excessive heat or in excessive moisture. Moderate warm and dry conditions are helpful when curing, so if it’s nice and sunny out, let them dry where they are,” says René Hardwick, director of public and industry relations for the National Onion Association. “Excessive exposure to moisture or sun in the curing process could lead to decay or collapsed layers,”

Alternatively, onions can be cured in a garage, backyard shed, or covered porch where they’re protected from wet weather. “The goal is to achieve dry conditions and temperatures below 85℉ for two to four weeks. Make sure whatever structure you’re curing your onions in has good airflow and ventilation. Open doors and use fans to move air around,” says Higgins.

How to Know When Your Onions Are Cured

You can tell when your onions are well cured when the outer skin layers dry to the point of making a rustling sound when they’re moved. “The necks of onions should dry down so that when you pinch the neck between your thumb and pointer finger, it feels dry and not slippery inside,” says Higgins.

When cured, brush off any remaining dirt and loose layers. Then cut the tops about an inch or so above the bulb (unless you want to braid the onions for storage), and trim the roots. Sort the onions and separate any that are damaged or haven’t cured sufficiently and use them right away (onion rings, anyone?).

How to Store Onions

“Ideal storage conditions for long-term storage is 32℉ with 65 to 70% relative humidity,” says Higgins. Although these conditions may be difficult to maintain at home, onions are pretty forgiving. “Often, storing cured onions in a barn or garage so that they cool down with the outside temperature is good enough,” says Higgins. Just be sure to avoid high temperatures and exposure to sunlight (which will trigger sprouting) and keep your storage area well-ventilated.

Store your onions on trays or in open bins to improve airflow around the bulbs and keep a watchful eye for bad bulbs or sprouts. Alternatively, you can store them in a mesh bag, wire basket, or crate. You could even braid them for hanging. Check them regularly and discard any that show signs of rot. Above all, don’t store onions near potatoes or apples. Spuds and apples can give off high levels of ethylene gas (a natural plant hormone), triggering spouting.

When you have a good harvest, it’s well worth the effort to cure and store your onions properly so you can continue to enjoy them for many months. That way, you’ll be prepared whenever the craving for onion dip or fajitas kicks in.