Corn is very susceptible to frosts. Look out for signs of frost to know if a cold snap will kill your crop. Corn doesn’t transplant well, either, so if you garden in a short-season area and want to start corn indoors, use biodegradable pots to avoid disturbing the roots at transplanting time. It’s better to wait until all danger of frost is past and the soil warms up to the 60 degrees needed for seed germination. If the weather stays cool, spread black plastic on the planting area to warm the soil more quickly.
If you want corn only for fresh eating, plant a minimum of 10 to 15 plants per person. To extend your harvest, sow an early-maturing type every 2 weeks for 6 weeks, or plant early, mid-season, and late types at the same time. To avoid cross-pollination, keep different corn cultivars (especially supersweets) 400 or more yards apart, or plant them so they tassel 2 weeks apart.
Site your corn patch in a sunny, wind-protected area. Corn is an extremely heavy feeder, especially on nitrogen, so it thrives in a place where soil-enriching crops like beans, hairy vetch, or clover grew the previous season, or add 20 to 30 pounds from the compost pile per 100 square feet to the soil as you prepare it for planting.
The best way to promote complete pollination is to plant corn in blocks rather than long individual rows — a block should be at least three rows wide. If you plant only one or two rows, hand pollinate to improve kernel formation.
For early plantings, sow seeds only 1 inch deep; in the hot weather of midsummer, plant them up to 2 inches deep. The average germination rate for sweet corn is about 75 percent, so plant three seeds together every 7 to 15 inches. They should germinate in 7 to 10 days. Thin to one plant every 15 inches. To avoid disturbing remaining plants, remove unwanted seedlings by cutting them off at soil level.
Corn can’t compete with weeds, so be sure to kill weeds thoroughly around the stalks for the first month of growth. After that, corn’s shallow roots will spread out as much as 1 foot from the stalk; be careful not to disturb these roots, because it’s easy to damage them. Instead, apply mulch to prevent weeds from sprouting.
Corn needs about 1 inch of water a week, particularly when the stalks begin to tassel. Water stress during pollination will result in ears with lots of missing kernels, so don’t skip watering your corn patch. Apply water at the soil surface by using a soaker hose or drip irrigation. Avoid spraying plants from above, which could wash pollen off the flowering tops.
When the stalks are 6 inches tall, side-dress them with blood meal or diluted fish-based fertilizer and repeat the feeding when they are about knee-high. Don’t remove any side shoots or suckers that appear; they won’t harm production, and cutting them might damage roots.
In order to produce kernels, wind must deposit pollen from the tassels (plant tops) onto each of the silks on the ears. Every unpollinated silk results in an undeveloped kernel. If you’re planting only a single or double row of corn plants, you can improve pollination by transferring pollen from tassels to silks yourself. Collect pollen as soon as the silks emerge from the ears and the tassels have a loose, open appearance. Wait for a morning when there’s no breeze, and shake the tassels over a dry bucket or other container to release the pollen. Collect pollen from several plants. Immediately transfer the pollen into a small paper bag and sprinkle the powdery material onto the silks of each ear in your corn patch. Repeat once or twice on subsequent days for best results.
Three weeks after corn silks appear, start checking ears for peak ripeness. Pull back part of the husk and pierce a kernel with your thumbnail. If a milky liquid spurts out, the ears are at prime ripeness — rush those ears to the table, refrigerator, or freezer. Ears on the same stalk usually ripen a few days apart. A completely dry silk or a yellow or faded-green sheath means the ear is past its prime.
Leave ornamental corn and popcorn on the stalks to dry until the first hard frost. If the weather is cloudy and wet, cut and stack stalks in a cool, dry place until the corn dries.