How To Tell When Corn Is Ready To Pick

Picking corn is done in two ways, dry harvesting and milk stage harvesting. Milk stage harvesting is done with sweet corn and the window for picking the corn is important. Dry harvesting is done with any other variety of corn like popcorn, decorative indian corn, field corn, or a flour corn. For dry harvesting wait to pick the corn until the husks, stalks, and tassels all turn brown.

You can get more specific with it if you want by taking an ear and testing the moisture content of it. For picking sweet corn use the milk stage harvesting method by puncturing a kernel near the middle of the cob and checking the liquid that comes out. Not too clear of a liquid but a milky liquid coming out is perfect. If no liquid comes out it’s past prime harvesting time. Don’t worry about kernels at the tip of the corn they don’t always mature and fill out.

For milk stage harvesting there are some signs to know that will let you know it’s time to start checking on it. About three weeks after the silks on the ears appear is harvest time. This can be faster, around two weeks, in warm areas with warm nights and as slow as four weeks in an area with cold nights. When you see silks that have withered and turned brown and have become more stiff and brittle than golden and pliable it’s a sign the ear is well pollinated and may be ready to harvest. Also the ear will be more plump than skinny around harvest time and the tip may be more rounded than pointed.

On the left is corn being left in the fields to dry, the dry harvesting method. On the left are ears that have become plump and the silks turned brown and withered up, a good time to check the corn using the milk harvesting method.

If you’re seeing these signs it’s time to take a closer look. Move the husk out of the way and take a look. The kernels should be well filled out. Next puncture a kernel near the middle of the cob with your fingernail. If the liquid that comes out is clear and watery it’s too early. Cover the ear back up and check again in a couple days. If it’s too viscous to run and little or no liquid comes out you’ve waited too long. Overripe corn will be less sweet and chewier. Milky and watery together and you’ve caught you’re sweet corn at the perfect time.

If you’re not going to cook the corn the same day as picking harvest sweet corn in the early morning before the sun has warmed the corn. By doing this the sugars in the sweet corn will convert to starch slower than if picked while the kernels are hot from the sun and the sweet corn will store longer.

How To Harvest and Store Corn

To pick the corn, grab the corn stalk above the ear with one hand. With the other grab the ear of corn and bend it downward until it snaps away from the stalk.

Fresh corn should be cooked within 4 hours after harvest for the best flavor. After this the sugar will begin to convert to starch and the more that process happens the less sweet the corn will be. You can store fresh corn in the refrigerator for up to a week. Always leave the husks on. Store in a breathable plastic bag like a produce bag or wrapped in damp paper towels.

To store corn long term you can blanch and freeze the corn either on the cob or off. Another option is to can the corn with a pressure cooker. Take the kernels off about 3/4 deep, don’t scrape the cob. If you want to can or freeze creamed corn take the kernels off at half the depth and then go back and scrape a little more or about another half off.

When Do Farmers Harvest Corn?

Here’s a cool map that shows every state’s typical start and end dates for corn harvest.

The first thing to know is that about 95% of the corn farmers are growing is field corn. As discussed above, field corn is left in the field to dry and the harvest time has a much wider window than sweet corn.

Farmers monitor the moisture levels of the corn to know when to harvest. There is a stage of the corn kernel development called black layer that lets the farmers know it’s time to start monitoring the moisture levels. Black layer develops at the base of the kernel and blocks any further starch development, ending any further growth of the kernels.

To test the moisture content of corn farmers will take kernels from various parts of the field and use a machine called a moisture tester or grain tester. You can see the moisture testers for sale here.

Farmers can’t store corn with a moisture content above 15% because the corn will mold with a higher moisture content. Also when selling the corn to the granary their pay will be docked if the moisture content is above 15% because the granary will have to dry the grain down to the 15% before storing and that takes fuel. At the same time the granary will not pay extra per bushel if the moisture content is below 15% so moisture content becomes very important to the farmers bottom line.

If corn is harvested too early they have high drying costs to get the moisture content down. If they leave field in the corn too long and try to let it dry to 15% they will have yield loss with plants falling over and ears falling off. So farmers will typically harvest corn with around 25% moisture content and use a grain dryer to get it down to 15%. The moisture content in the field will be affected by temperature, rainfall, and humidity levels.

On the left is sophisticated corn storage structures. Without a doubt there is a structure for grain drying nearby. On the right is rudimentary drying of corn.

How Long Does It Take Farmers To Harvest Corn?

As you can see from the map above it typically takes farmers around two months to harvest their corn crops. The combine is the machine that picks in the field and it runs at about 4 MPH. When the combine is full it has to take its load of corn to a semi-trailer or grain cart and unload it. Some areas of the country with more forest have lots of small fields and have to take equipment from one field to another which takes time.

The farmers only have so much on site storage and drying capacity so sometimes this creates a holdup in the process as corn needs to be taken to the granary to free up space for more corn. Bad weather can put a stop to the harvesting as the combines will damage the field causing compaction of the soil if run on muddy soil. Breakdowns of machines can also cause delays. Here’s a great article with videos that show how a combine works to harvest the corn.

How To Harvest Seed Corn

To harvest corn for seed leave the cob on the plant until the husk turns brown. Then pull the ear off the stalk and take the husk off. The kernels should be wrinkled and withered looking from dehydration. Let the cobs of corn dry in a cool dark place for a week or two. Preferably hang them by a string in the open air. Wring the cob like you’re giving it an indian burn to get the kernels off. Discard any discolored kernels.

If you’re growing corn for seed corn on purpose and didn’t just accidentally leave the corn on the plant too long, oops! You’ll want to be careful to avoid cross pollination. The best way to avoid cross pollination is to place a bag over the ears of corn before the silk develops so that they won’t catch any pollen until you want them to. Then take pollen from the tassel of the variety you want to pollinate them with and hand pollinate the silks. Put the bag back over it to keep cross pollination away. Check out this article for more on pollination.

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