Popcorn is a specific type of maize that possesses a hard, moisture-retaining hull necessary for the explosive reaction that creates the fluffy snack. Unlike sweet corn, which is harvested while the kernels are still soft and milky, popcorn harvest timing depends on achieving a precise low moisture content. The goal is to allow the kernels to dry on the stalk for as long as possible to reduce initial water content, a process distinct from the curing that must follow. This need for a specific, low-moisture state makes the harvest and post-harvest process for popcorn different from other corn varieties.
Identifying Peak Maturity in the Field
The readiness of the popcorn crop is determined by visual and physical changes in the late summer or early fall. The first sign is the complete drying of the husks, which transform from green to a brittle, brown or yellow color. This indicates the plant has stopped supplying moisture and nutrients, allowing the natural drying process to begin. Allowing the ears to dry on the stalk for as long as the weather permits yields the best final result.
The entire stalk should also be drying out and losing all its green coloration before harvest. If the stalks are still green, the kernels are not yet mature. To check the kernels, pull back the dry husks and perform a “thumbnail test.” Mature kernels should be very hard and glossy, and you should not be able to easily dent them with your fingernail.
Harvest the ears before a hard freeze or a prolonged period of wet weather sets in, which could lead to mold or rot. The timing is often based on local weather, usually occurring in mid-to-late fall. While maximizing field drying is the goal, a balance must be struck to avoid damage from heavy rain or pests.
The Harvesting Procedure
Once the physical signs of maturity are evident, begin harvesting by twisting the ears cleanly off the stalk. Handle the ears with care to avoid damaging the kernels, which compromises popping quality.
Gardeners have two primary methods for preparing the ears. Some pull the husks back but leave them loosely attached, allowing the ears to be tied together for hanging. Alternatively, the husks can be completely removed, or “shucked,” before curing. Shucking the ears immediately allows for better air circulation during the subsequent drying phase.
The Essential Post-Harvest Curing Process
Popcorn is not ready to pop immediately after harvest because the moisture content is still too high, often around 20% to 30%. Popping requires internal moisture to be rapidly heated into steam, building pressure to fracture the hard outer hull. If the moisture content is too high, the kernel will not pop fully or may result in a chewy texture.
For the best popping quality, the moisture content must be reduced to an ideal range of 13.5% to 14.5%. This reduction is achieved through post-harvest curing, a controlled, slow drying period in a protected environment. Curing involves placing the shucked ears in mesh bags or hanging them in a location with good air circulation.
The drying location should be cool, dry, and well-ventilated, such as a garage, shed, or basement, to prevent mold or mildew. Curing usually spans four to eight weeks, depending on initial moisture and humidity. This slow drying ensures moisture leaves the kernel gradually while maintaining the integrity of the hull. If the corn dries too quickly, the hull can crack, leading to poor popping expansion.
Testing Readiness and Long-Term Storage
The only reliable way to determine if curing is complete is by performing a small-scale “test pop.” Shell a small handful of kernels from a cured ear and attempt to pop them using your preferred method. If the test batch results in a high percentage of popped kernels with good expansion and a crisp texture, the popcorn is ready.
If many kernels fail to pop, or if the resulting popped corn is small and chewy, the kernels are still too wet and require more drying time. Conversely, if the popcorn shatters or results in many “old maids,” the kernels may have become too dry, dropping below the 11% moisture threshold. Once the test pop is successful, shell the remaining corn by rubbing the kernels off the cob.
To maintain the optimal moisture content and preserve popping quality, store the shelled kernels in airtight containers, such as glass jars with tight-fitting lids. This seals in the current moisture level, protecting the kernels from fluctuating humidity. Keep the containers in a cool, dark environment, where the popcorn can maintain its flavor and popping performance for several years.