Determining the precise time to harvest is a blend of observation and understanding the plant’s biology. Correct timing is necessary for successful long-term preservation, as harvesting too early or too late can compromise the bulb’s integrity and storage potential. The goal is to capture the bulb when it has maximized its size and the plant has signaled its natural dormancy.
Recognizing the Visual Signs of Maturity
The clearest and most reliable indicator that an onion is ready for harvest is the natural collapse of the green tops, a process known as “lodging.” Lodging begins when the neck of the plant softens and can no longer support the weight of the foliage. This signals that the plant is diverting energy and nutrients down into the bulb for final development.
The natural falling over of the tops signals that the transfer of carbohydrates into the bulb is complete. Wait until 85-90% of the tops in your patch have flopped over before beginning the harvest. Once lodging has started, stop watering the plants to encourage the outer skins to dry and prevent rot. The visual cues of the tops falling over remain the definitive sign for all bulb onions.
The Crucial Step of Curing
Once the mature bulbs are gently lifted from the soil, the immediate next step is curing, a process that is necessary for long-term storage. Curing serves to dry the outer layers of the bulb and, most importantly, to seal the neck where the foliage was attached. This sealing creates a protective barrier against moisture loss and prevents microorganisms that cause decay, like neck rot, from entering the bulb.
To cure onions properly, leave the tops intact and spread them in a single layer in a warm, dry location with excellent air circulation. A covered porch or well-ventilated garage is an ideal setting, protecting the bulbs from direct rain and sun. This drying process typically takes between one to three weeks. Curing is complete when the outer skins are papery and the neck is completely dry and tight.
Proper Storage for Longevity
After the curing process has dried the onion’s neck and skin, the bulbs are ready for preparation and transfer to their long-term storage location. Before storing, trim the dried tops to about an inch above the bulb, and clip the roots short. Place the prepared bulbs in a breathable container to ensure continuous air circulation, such as:
- Mesh bags
- Slatted crates
- Old pantyhose
The ideal environment for maximizing onion longevity is a cool, dry, and dark space, with temperatures maintained between 32 and 40°F (0-4°C). Low humidity is important to prevent moisture from compromising the outer skins and encouraging sprouting or decay. Pungent onion varieties stored under these conditions can be successfully kept for several months.