Onion harvesting in Ohio is a process driven by the region’s photoperiod—the length of daylight—which directly influences bulbing. Ohio is considered a “long-day” growing region, meaning the onions planted here require 15 or more hours of daylight to properly form bulbs. Successfully storing onions for months relies entirely on a precise harvest schedule and a proper post-harvest drying procedure. The goal is to maximize the bulb’s maturity while ensuring the neck seals completely, which protects the onion from moisture and decay-causing organisms.
Identifying Harvest Readiness
The primary indicator that storage onions are ready for harvest is a clear visual change in the foliage. Gardeners should watch for the point when approximately 50% to 75% of the onion tops have naturally fallen over and begun to yellow or brown. This natural lodging of the tops signifies that the plant has ceased its active growth phase, and the transfer of sugars and nutrients from the leaves to the bulb is near completion.
A more specific sign of maturity for storage is a physical softening of the neck, which is the area where the leaves meet the top of the bulb. This softening indicates the final cell division in the rings is finished, and the neck is preparing to dry down and seal the onion. Harvesting before this stage means the bulb has not fully accumulated its storage-enhancing compounds, while waiting too long increases the risk of the neck splitting or the onion becoming over-mature. The typical harvest window for long-day onions in Ohio usually falls in late July through early September.
Essential Pre-Harvest Steps
To encourage the necessary neck-softening and subsequent drying, gardeners must alter their cultural practices in the one to two weeks leading up to the expected harvest date. The most important action is to stop all irrigation and cease fertilization entirely during this period. Allowing the soil to dry out helps to initiate the natural senescence, or aging, of the onion plant and its foliage.
This reduction of moisture is a deliberate step to begin preparing the bulb for dormancy and storage while it is still in the ground. A dry environment encourages the neck to thin and soften, which is the plant’s natural process for sealing the bulb from the outside world. This dry soil condition also minimizes the risk of rot and fungal diseases.
The Physical Act of Harvesting
When the signs of maturity are evident, the onions must be removed from the ground with care to prevent bruising, which is a common entry point for rot and decay organisms. It is best practice to gently loosen the soil around the bulbs using a garden fork or spade before lifting them out. Simply pulling the bulbs by the tops can cause the neck to tear, creating a wound that will not seal properly and will lead to quick spoilage in storage.
After the onions are lifted, any large clumps of soil should be brushed off, but the bulbs should not be washed, as introducing moisture will impede the curing process. The roots can be lightly trimmed at this point to about a quarter-inch, but the tops must remain attached to the bulb. The onion should be handled gently and immediately moved to a safe location for the next critical step.
Curing for Long-Term Storage
Curing is the non-negotiable process that hardens the outer skin and dries the neck, transforming the fresh bulb into a storable commodity. This procedure requires a warm, dry, and well-ventilated location, such as a covered porch, shed, or garage, where the onions are protected from rain and direct sunlight. The ideal curing temperature range is between 75°F and 85°F, with good airflow being paramount to prevent mold and mildew.
The bulbs should be spread in a single layer on screens, racks, or wooden crates to ensure air circulates completely around each onion. This drying phase usually takes between two and four weeks, depending on the ambient temperature and humidity. Curing is complete when the outer skins are papery and rustle when touched, and the neck is completely dry, tight, and shriveled. Once fully cured, the dried tops can be trimmed to about one inch above the bulb, and the remaining roots should be clipped close to the base.