Yellow onions are a staple crop, cultivated for their flavor and ability to be stored for extended periods. The longevity of these bulbs results from careful agricultural timing. Maximizing storage potential and flavor depends entirely on knowing exactly when to lift the bulbs from the soil. This timing marks the moment the plant ceases energy production and prepares for dormancy.
Visual Cues for Harvest Readiness
The precise time to harvest yellow onions is signaled by the plant itself, not by the size of the bulb. The most recognizable sign is the “neck fall,” which occurs when the green tops begin to yellow, wither, and collapse over near the bulb. This flopping indicates that the transfer of carbohydrates from the leaves to the bulb has concluded, signifying full maturity.
Growers typically wait until 85% to 90% of the plants have tops that have fallen over before harvesting. Another indicator is the softening of the neck tissue where the leaves meet the bulb. A mature onion’s neck will feel soft and pliable, having stopped its internal growth processes.
Cease watering the plants one to two weeks before the anticipated harvest. This encourages the final stages of maturity, preventing the bulb from reabsorbing water and reducing the risk of rot during curing and storage. Harvesting before the foliage dies back completely significantly reduces the bulb’s ability to store well.
Lifting the Onions from the Soil
Removing the bulbs from the ground requires care to avoid damage that compromises long-term storage life. Instead of pulling them by the tops, which can detach leaves or bruise the neck, use a garden fork or spade. Insert the tool several inches away from the bulb to gently loosen the surrounding soil.
Lift the onions carefully to keep the outer layers intact, as bruising or cuts can invite rot and disease. Once loosened, gently pull the bulbs from the soil, leaving the tops and roots attached. Immediately after lifting, leave the onions in the field for a brief, initial dry-off period, provided the weather is clear and dry.
Laying the harvested bulbs on the soil surface for a day or two allows excess moisture to evaporate and dirt to dry, making it easier to brush off. This initial drying prepares the bulbs for the more extensive curing process. If rain is expected, move the bulbs immediately to a protected area.
Curing Onions for Long-Term Storage
Curing is the most important post-harvest step for ensuring yellow onions can be stored for months. This process involves thoroughly drying the outer skins and the neck, creating a protective, sealed barrier against moisture loss and microbial entry. The ideal environment for curing is well-ventilated, dry, protected from direct sunlight, and warm, with temperatures maintained between 75°F and 85°F.
The bulbs can be spread out in a single layer on screens or racks, or braided by their tops and hung up for maximum air circulation. This warm, dry air flow encourages the neck tissue to completely dry and shrivel, forming a tight seal that prevents pathogens from entering the interior. The outer layers also dry out, becoming the familiar papery skins.
Curing typically takes between two and four weeks, depending on temperature and humidity. Curing is complete when the outer skins are thin and papery, the roots are dry and brittle, and the neck is completely sealed and dry to the touch. Once fully cured, the dried tops and roots can be trimmed, leaving about an inch of the neck attached.
Conditions for Successful Onion Storage
After curing, the onions must be moved to an environment optimized for dormancy to ensure months of freshness. The ideal long-term storage conditions are cool and dry, specifically a temperature range of 32°F to 40°F with low humidity. Temperatures above this range can cause the bulbs to break dormancy and begin sprouting, while excessive moisture encourages root growth and mold development.
Proper ventilation remains crucial during storage to prevent moisture buildup around the bulbs. Cured onions should be stored in porous containers that allow air to circulate freely, such as mesh bags, braided bundles, or slatted crates. Storing them in a dark location also helps maintain dormancy by preventing light exposure that can trigger sprouting.
When stored correctly in these cool, dry, and dark conditions, yellow onion varieties can maintain their quality for six to twelve months. Regular inspection of the stored bulbs is recommended. Any soft or damaged onions should be removed immediately to prevent the spread of rot to the surrounding healthy crop.