Sweet Corn, Small Areas

By: Dr. Nancy Roe
Sweet corn is a crop that is not usually recommended for small home gardens. While it is true that the production per unit area is not as high as crops which produce many fruit over a longer season (such as tomatoes and peppers), you can grow a surprising amount in a relatively small area. For instance, four rows that are 10 feet long will require about 100 square feet and should produce four to five dozen ears. However, producing maximum yields requires careful management of all the factors.

Normal good garden site selection and soil preparation are important: choose full sun location, have your soil tested, and add organic matter (compost is the best). Raised beds will help with drainage and warm up the soil early in the spring. The easiest way to water is to lay or bury a drip irrigation tape beside each row.

Fertilize based on soil test recommendations. Remember that corn is in the grass family, so it needs lots of nitrogen, especially early in the season. However, unlike our turfgrasses, we want it to produce seed, so you may also need to add phosphorous and potassium, based on your soil test results. Do not try to add all the fertilizer at once, though.

Till in a third to half of the nitrogen and potassium and all the phosphorous. Sidedress with nitrogen several times during the first four to six weeks. However, if you garden in a very sandy soil, it is best to add the potassium in stages with the nitrogen, too.

Also, if you are using a complete fertilizer, apply in stages (i.e. one third at planting, one third when the corn is knee high, one third when corn starts to tassel). Organic fertilizers can generally be added earlier as those forms of nutrients are not as subject to loss through leaching and may take longer to become available to the plant.

If you have a drip irrigation system, you can inject fertilizer once or twice a week. Lime may be needed in acid soils, primarily East Texas. Corn can also sometimes show chlorosis (yellow and green striped leaves) in an alkaline soil, due to inability to take up enough iron. However, an addition of 2 to 4 inches of compost tilled into the soil before planting should help to prevent that problem.

Planting dates can be tricky. Sweet corn does not germinate well if soil temperatures are below 55 degrees (60 for the supersweet varieties) and grows best at 75 to 85 degrees. But, high night temperatures are not good, either. So, for spring crops we try to plant the normal varieties about the time of average last frost. For fall, plant 12 to 14 weeks before average first frost. Seed can be spaced as closely as 6 to 8 inches apart in rows 28 to 32 inches apart.

Planting pattern is very important for corn. It is pollinated by wind, which moves the pollen from the "tassels" to the silks. Since each silk leads to a kernel, each must receive pollen. Therefore, corn planted in long single rows does not usually receive the proper pollination and produces ears which are not "filled out." Plant your corn in shorter rows, forming rectangular "blocks."

Early in the season, cultivate and pull weeds as they germinate to prevent competition with corn seedlings. After a few weeks, corn should out-compete most weeds.

A big question with corn is whether or not to remove the suckers. While opinions differ, it is usually not worth the trouble.

VARIETIES

Most traditional Texas gardeners grow field corn and harvest the ears while young. In Texas conditions, that is the easiest way to go because field varieties are more tolerant of cool spring conditions. However, many agree that sweet corn does taste better, and choosing the best-adapted varieties can help you to be successful with it. Most of the tall, long-season varieties which are grown in the north do not do well in Texas conditions. Look for early varieties (those that mature quickly) so you can fit them in during the spring or fall season. Choose white, yellow, or bicolor, depending on your preference. There are three types to choose from - each have advantages and disadvantages (see "The Sweet Truth About Sweet Corn," January/February 1999 issue).

Ever heard the old saying about getting the water boiling on the stove before you harvest the corn? That refers to the oldest type, called su or normal sugary. These are the varieties most of us know. Once harvested, the sugar in their kernels begins to turn to starch immediately. They are also generally the easiest to grow. Some of the best are: Golden Queen, Guadalupe Gold, Merit (yellow varieties); Sweet G-90, Honey & Pearls (bi-color varieties); Silver Queen, Frontier (white varieties).

These (sugary enhanced) varieties have higher levels of sugar. They also have very tender kernels, which means they do not ship well but are great for home use. I have actually had people tell me that some of these are too sweet! Kandy Korn is one of the original ones.

The sh2 or supersweet varieties are not only sweet but sugar continues to be produced after harvest. These varieties must be isolated from other corn varieties, or they will taste like field corn. They are also more difficult to grow. Germination rates are usually lower than other varieties. They will not grow in cool soils and seedlings are often weak even under warmer conditions. Look for the early (short-season) varieties, because you cannot plant them too early in the spring.

By far the worst pest of sweet corn is the corn earworm. This moth lays her eggs on the silks, and the larvae make their way into the ear where they feed. Many people do not even attempt to control them, preferring to cut out the damaged area of the ear. However, if you wish to be conscientious, you can get pretty good control. Look for varieties with a tighter fitting shuck. The Bacillus thuringiensis (BT) products will kill corn earworms if you can get it where they are feeding - inside the shuck! Some gardeners use mineral oil applied with a dropper on the silks to prevent the worms from entering the ear. One of the Sevin(tm) products that is labeled for sweet corn will usually be effective. Any of these treatments must be used every two to three days once silking begins. However, be sure to stop for the proper interval before harvest if the label directs that.

To really use your garden space efficiently, experiment with intercropping and succession cropping in your garden. As the ears begin to form, plant seeds of warm season cucurbits such as watermelons or pumpkins between stalks. Or, take out every second or third row of corn and leave the others standing as shade for fall tomatoes and peppers that you are planting in July.

The most accurate way to tell if corn is ready is a very old one: peel back the shuck, and break open a kernel. If the "juice" inside it is milky, it is time to harvest.

One important tip for the best tasting sweet corn: do not overcook it! I like to steam it rather than boil, and for no more than seven minutes. I find that it does not even need butter or salt - while you may not agree with this, I think you will agree that sweet corn is worth including in your garden!