Corn: A Growing Guide

 
Corn is more American than apple pie: It’s been cultivated in North American gardens for more than 4,000 years. Even though it takes a large share of garden space, many gardeners make room for sweet corn because of the unbeatable sweet, corny taste of fresh-picked ears.

The sugar in the kernels of ears of open-pollinated sweet corn varieties starts changing to starch almost as soon as you pick the ears. However, plant breeders have developed dozens of new and ever-sweeter cultivars that retain their sugar content for days. If sweetness is your prime goal, choose varieties listed as supersweet (abbreviated as sh2 in seed catalogs), but keep in mind that these may not be as vigorous as other types of sweet corn. If you prefer good old-fashioned corny flavor, pick standard (su) varieties. For a compromise of sweetness and vigor, choose sugary-enhanced varieties (se). Or, if you like to experiment with the latest innovations, try planting a synergistic variety. These varieties produce ears with a combination of sugary-enhanced kernels and supersweet kernels on each ear. Whichever type you decide to grow, it’s a good idea to check with other local growers or your Cooperative Extension service to see what varieties have a good track record in your area. 

 

If you have lots of garden space, you may also want to try growing some popcorn or ornamental corn, which has similar planting and care needs as sweet corn.

 

Planting: Corn is very susceptible to frosts. You can lose a crop if you plant too early. 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°F 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 of compost 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, as described on the next page.

 

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.

 

Growing guidelines: Corn can’t compete with weeds, so cultivate 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.