To harvest corn, simply tear the ears from the corn stalk. Because all the ears on a stalk of corn are usually ready for harvesting at the same time, it is not important to avoid damaging the stalk. Harvest corn 20 days after the first silk appears on the ears.
The best time to harvest corn or any other vegetable is early in the morning. During the early morning hours, the corn plant has not yet converted its sugars into starches, so corn harvested at these hours is sweeter than corn harvested later in the day. While 20 days is a good benchmark to use for harvesting corn, do not harvest more corn than you intend to eat or preserve all at once. Corn remains edible on the stalk up to 30 days after the first silk appears.
Make sure corn is ready to harvest by puncturing an individual kernel with a needle or sharp knife. If the kernel produces a milky white liquid, it is ready to harvest. If it produces a clear liquid, it requires more time on the stalk. If puncturing the kernel produces no liquid at all, it has remained on the stalk too long.
Corn used for seed, decoration or animal feed must be left on the stalk much longer. Leave these ears on the stalk until they get hard and starchy, but remove them before they begin to rot.