The process of drying onions from the garden, often called curing, is necessary to transition the fresh bulb into a storable commodity. This procedure involves sealing the neck and drying the outer layers, which concentrates the flavor and creates a protective, papery skin. Proper curing develops a natural defense against moisture loss and pathogenic microorganisms, the primary causes of rapid spoilage. Skipping this phase leaves the onion’s moist neck vulnerable to rot, drastically reducing its storage life.
Knowing When to Lift Your Onions
The timing of the harvest is determined by distinct visual cues from the plant’s foliage. Onions signal readiness when their green tops begin to yellow, soften, and naturally fall over. This flopping indicates the plant has stopped transferring energy and has begun bulb maturation and skin development.
Wait until at least half to three-quarters of the onion tops have bent over before harvesting. Pulling bulbs too early results in thick necks that will not seal properly, leading to storage issues. Leaving them in the ground too long can increase the risk of rot or encourage new root growth.
A week before harvest, reducing or stopping watering helps to toughen the skins and prepares the bulbs for drying. Once the signals are met, lift the onions carefully from the soil to avoid bruising, which compromises storage potential. Use a garden fork to gently loosen the soil a few inches away from the bulbs to prevent damage during extraction.
After lifting, gently brush off any large clumps of soil. Avoid washing the onions, as introducing moisture is counterproductive to the drying process.
The Curing Process for Long-Term Storage
Curing hardens the outer scales and seals the neck of the onion, preparing it for extended storage. This process requires warmth, low humidity, and excellent air circulation. The ideal temperature range is approximately 75–85°F (up to 90°F), with relative humidity kept below 70%.
The onions must be spread out in a single layer, ensuring the bulbs are not touching, which allows air to circulate completely around each one. Wire racks or mesh screens work better than a solid floor because they permit airflow from below. This setup facilitates the removal of moisture from the outer layers and the neck, which is the last part of the onion to fully dry.
The curing process typically lasts between two to four weeks, depending on the temperature and humidity. Curing is complete when the outer skins are thin and papery, the roots are shriveled and brittle, and the neck is completely dry and tight. A dry, constricted neck indicates the natural seal has formed, preventing pathogens from entering the bulb.
If the weather is wet or overly humid, cure the onions in a covered, well-ventilated area like a shed or garage, away from direct sunlight. Direct sun can cause sunscald, while high humidity encourages mold and rot. Using a fan to create a continuous breeze improves air circulation and accelerates drying.
Trimming and Final Storage Methods
Once the onions are fully cured, they must be prepared for long-term storage. The neck should feel completely dry and shriveled, indicating a successful seal. At this stage, the dried roots can be trimmed off close to the basal plate.
The dry foliage should also be trimmed, leaving a small stem of about one to two inches above the bulb. Leaving this short, dry stem maintains the integrity of the protective neck seal, which prevents storage rot. Any onions with a thick, moist neck or visible damage should be set aside for immediate consumption, as they will not store well.
For long-term preservation, cured onions require a cool, dark environment with low humidity and continued air circulation. The optimal storage temperature is near freezing, typically between 32–40°F, to prevent sprouting. Low humidity, ideally 60% or less, is necessary to discourage the growth of roots or mold.
Storage containers should allow for maximum airflow. Mesh bags, shallow crates, or baskets are excellent options. Onions can also be braided together by their dry tops and hung, a traditional method that ensures excellent ventilation. They should be stored away from potatoes, as the moisture and gasses released by potatoes can cause onions to spoil faster.