Gardening Basics: Corn

Planning Your Corn Crop
By: National Gardening editors
If you've never grown corn before, check with a local farm or garden store, a neighbor who raises corn or your Cooperative Extension Service agent before you buy seeds. They can tell you what varieties do particularly well in your area, as well as some of the disease, pest or weather problems you may encounter.

Corn Varieties

When asking for advice, keep in mind that gardeners are often emotionally attached to their favorites. For instance, some people always plant Silver Queen corn, even though the first, creamy white ears won't be ready to harvest until fall. That waiting is part of what makes 'Silver Queen' special, and the long-awaited fall harvest is one of life's fine pleasures. Other people feel the same about 'Country Gentleman' or 'Stowell's Evergreen'.

Sweet corn varieties are usually grouped according to the length of their growing season. You can really extend your harvest by planting more than one group at the same time. The tassel time won't overlap, so you won't have to worry about cross-pollination between varieties.

Despite the preference for a particular type of corn, it's a lot of fun to try a new variety or two every year. However, although the latest hybrids often produce beautifully, watch the results of a few seasons before you depend on a new one for your main crop.

Common Sense and Cross-Pollination

You may come upon words of caution in a seed catalog or have had another gardener tell you to isolate certain types of corn to avoid cross-pollination. It's true that corn's dependence on the wind for pollination means you sometimes have to watch out for accidental mixing of different varieties, but in most home gardens this is a minor problem, if one at all.

The technical explanation for the way corn changes when it's pollinated by another variety has to do with recessive and dominant genes, plus a number of other factors. Luckily, you don't have to be a plant breeder to understand how to keep your garden corn from having an unwanted mix-up. You can just use common sense.

When one type of corn tassels - letting its pollen loose - that pollen can land on the silks of any corn in the immediate area. If only one variety of corn is silking at any given time, crossing cannot take place. This is usually the case in home gardens, where the varieties planted tend to have significantly different flowering and growing seasons.

If two similar varieties cross, the difference in the resulting ears may be unnoticeable. However, because of their genetic makeup, some types of corn suffer if they cross with a stronger or dominant variety.

What's a Home Gardener To Do

There are three instances where this can be a concern in the home garden. First, yellow corn is dominant over white. If a yellow and a white variety cross, the white corn could end up with some yellow kernels. Because it's dominant, yellow corn wouldn't be affected by the cross.

Second, both popcorn and field corn have genes that are dominant over sweet corn. If a cross takes place with either popcorn or field corn and sweet corn, the sweet corn is likely to be tough and starchy. Again, because they're dominant, popcorn or field corn wouldn't be affected by the cross.

Third, many of the genes for supersweet flavor are recessive, so they're affected by any corn that crosses with them. That's why the seed companies advise isolating these varieties.

Corn Isolation

Isolating just means preventing an unwanted cross, and you have a choice of ways to do this. All you have to do is prevent cross-pollination. Simply plan to keep different varieties of corn that enter the tassel and silk stage at the same time far enough apart that their pollens won't mix. The recommendations vary from 100 feet to 600 feet, depending on whom you ask. Naturally, the farther apart the better, but about 200 feet is fine unless you regularly experience very strong winds.

To isolate corn you can choose varieties with different days to maturity, or stagger plantings of varieties that have a similar number of days to maturity. Allow at least 10 days between plantings, and your crops shouldn't cross.

Another trick is to plant the dominant corn on the prevailing downwind side of any variety that will suffer if they cross. If you're not sure in which direction the prevailing winds blow in your area, check with your local weather service.

Some gardeners claim that planting a "fence" of two rows of tall sunflowers between corn varieties is enough to prevent cross-pollination. This works most of the time, because the odds are generally in your favor when it comes to accidental crossing.

Old Favorites

An open-pollinated corn variety is a nonhybrid or a strain that has grown for many generations without plant breeders' modifications. With the revived interest in heirlooms, many other varieties such as 'Country Gentleman', 'Golden Bantam', 'Stowell's Evergreen', and 'Ashworth' are becomming more readily available to home gardeners.

Open-pollinated corn grows just like its parent plants, so you can save the seed from one year to the next with good results. If you want to save the seeds of an open-pollinated variety, isolate the crop from other varieties, so there won't be an accidental mixing of pollens to affect the next generation.
Corn: Planting Basics
By: National Gardening editors
There's an old farmer's rhyme about planting corn seed: "One for the blackbird, one for the crow, one for the soil and one to grow."

Although it's not necessary to plant four times the amount of seed that you actually want to grow, a little extra doesn't hurt, if only to ensure good germination. As for the blackbird and the crow, they may be tough to beat in large cornfields, but there are a few ways to outwit them in the home garden.

Planting Methods

Once the seedbed is well worked and fertilized, you're ready to plant. There are two traditional ways to plant corn: three to five seeds grouped together in small circles, or "hills,"or spaced evenly down straight rows, one behind the other.

Many people find that planting corn in rows takes less time. There's usually less thinning needed, and it's easy to cultivate rows during the season. To plant in rows, stake each row the length you want and stretch a string along the ground to mark the planting line. Use the edge of a hoe or the end of its handle to draw a shallow furrow, one to two inches deep, along one side of the string. A handy way to fertilize the row at this time is to draw a second shallow furrow down the other side of the string. Sprinkle a band of fertilizer in this furrow. When it's time to cover the seeds, one pass with a hoe will cover the fertilizer at the same time.

How To Plant

To plant, just drop seeds into the planting furrow, spacing them 8 to 10 inches apart. Firm the seeds into the soil with the back of a hoe to keep the seeds in place. This allows good contact with the soil, which is important for germination.

Next, cover the seeds with one to 1 1/2 inches of soil. You can draw the hoe along the string to flatten the ridge of soil created by making the furrow. This automatically brings the planting and fertilizer furrows to ground level, covering the seeds and fertilizer with the right amount of soil. You can also cover corn seeds by raking one to 1 1/2 inches of soil over them, using soil from the edges of the furrow. Firm the soil one more time after covering.

Leave 24 to 36 inches between the rows for cultivation, and plant at least four rows for the best pollination. Many short rows will provide better pollination than just a few long ones. If you intend to weed and cultivate the corn rows with hand tools, you don't need as much room between the rows as you do if you plan to cultivate by machine.

Planting in Hills

To plant in hills, stake out the rows, but don't make the straight-line planting furrow. Instead, every 18 to 24 inches, use your hoe to draw a circular planting furrow, about six inches in diameter. Place a small handful of fertilizer to the side of the seeds and cover it. Plant three to five seeds in each circle. Firm the seeds, cover with one to 11/2 inches of soil and firm again.

If all the seeds in each hill come up, you'll have to thin out all but the two or three strongest or the seedlings will be too crowded. If you don't like to thin corn, don't plant in hills. However, plenty of gardeners don't mind hand thinning. Try planting both ways and decide for yourself.
Corn Care
By: the Editors of National Gardening
Corn doesn't need any more attention than other garden vegetables, but it's a crop that can take up a fair amount of time if you plant a lot. Make it easier by combining tasks. For instance, when you side-dress, pull any weeds you see, or side-dress at the same time you hill the rows.

Weed Control

Like any plant, corn produces better if it doesn't have to compete with weeds. It's especially important to keep weeds out when corn plants are young. Once the stems and leaves are established, they can tolerate weeds better. Plus, the stems and leaves of larger corn plants shade the soil somewhat to block out weeds.

Weed your corn every few weeks, starting before you even plant a seed. Work the soil several times before planting. This not only conditions the soil, it stirs up and kills tiny weed seeds lurking near the surface. It also buries some seeds so deeply that they never get a chance to sprout.

Once the corn is planted, scratch the surface of the planting bed every week or so with a weeding rake. When the corn is tall enough to be hilled, you'll automatically get rid of weeds by covering them with soil as you hill.

Hilling

Hilling is pulling up soil to mound it around the base of a plant. When you hill a young corn plant, the added soil around its stem helps support it as it grows taller. This protects it from being blown over in a strong wind. To really anchor plants, it's a good idea to hill corn every two to three weeks until the plants start to tassel.

Hilling also covers and smothers any weeds around the base of your corn plants. You might say you're creating a "soil mulch" around your plants. If dryness is a problem, extra soil helps the corn roots retain moisture.

You can hill with a hoe by scooping a few inches of soil from the walkways into loose mounds on both sides of the corn. If you want, you can hill your corn by machine, using a tiller with a special hilling attachment. This is both faster and easier than using a hoe, and it also does a uniform job.

Side-dressing

The more you feed corn, the more it will feed you, so side-dressing (a second dose of fertilizer that boosts growth) is a must with corn.

You can use any high-nitrogen fertilizer to side-dress corn, because nitrogen is the plant nutrient needed. A commercial fertilizer such as 10-10-10 works well, but you can also use well-composted or dehydrated manure, or commercial organic fertilizers like cottonseed meal.

Side-dress corn twice: when it's knee high and when it tassels. To side-dress, sprinkle a thin line of fertilizer or manure about four inches from the plants on both sides of each row of corn. To side-dress hill-planted corn, simply sprinkle fertilizer around each hill, about four inches away from the cornstalks. It often helps to make a shallow furrow first for either rows or hills. The furrow serves as a guide and the indentation helps the fertilizer stay put.

If you side-dress shortly before it rains, you're lucky. Otherwise, you should water, so the fertilizer leaches into the soil where it can be taken up by the corn roots.

Watering

Corn doesn't need more water than other vegetables. It just suffers more if the supply runs short. The plants are relatively tall and exposed to the wind and drying heat of summer, so they often "transpire" or give off moisture faster than their roots can take it up.

Corn's need for water is most critical from the time it tassels until the ears are ready for harvest. At this time, the plant is devoting all its energy to seed production, holding nothing in reserve for a dry spell.

During its growing season, corn needs at least an inch of water per week. If it has to go through a dry stretch, it may not produce well. Use a rain gauge to keep track of weekly rainfall. If your garden receives less than an inch of rain in a week, water.

When you water, water thoroughly. If you're using an overhead sprinkler, use your rain gauge to determine how long it takes to deliver an inch of water. Or, simply water until the soil feels moist three to five inches down, depending on your soil type. (Sandy soil absorbs water faster than clay.) One sign of too little water is the corn leaves curling or rolling. If you want healthy, sweet, well-filled ears, pay close attention to the weather at the tail end of the season and water if your corn needs it.

If you have the equipment, it's most efficient to water corn with a soaker or drip irrigation hose, or to use furrow irrigation. A soaker hose is made of a material such as perforated canvas that lets water seep out slowly. Drip irrigation has lines running straight to each plant that constantly drip a small amount of water to the roots. If you water directly from a hose or bucket into a furrow, it accomplishes the same beneficial watering at the base of the plant. With these watering methods, less water is lost to evaporation than if you use an overhead sprinkler. The water doesn't end up on the leaves of tall corn plants, instead it's near the roots where it's really needed.
Harvesting Corn
By: the Editors of National Gardening
Harvesting corn is a matter of picking the ears at peak flavor. Here's how to know when to harvest.
The Sweetness Factor
The prime harvest time for sweet corn passes quickly for most varieties except the supersweets, so gardeners need to know how to judge when to harvest to get the most from their crop.
Corn is ready to be picked as soon as the ears have completely filled out. This goes for sweet corn and roasting ears.You can tell when this happens by feeling the end of an ear. If it's rounded or blunt rather than pointed, the ears are ready. The silks also dry up when the ears are almost ready to be picked.
If you don't trust your judgment, you can pull back a bit of the husk and check to see if the ear looks well filled and the kernels are creamy yellow or white. Many gardening guides tell you to pierce a kernel with your thumb nail to test for ripeness. If the liquid inside is watery, that ear isn't quite ready. If the liquid is white or "milky," you're in business.
Although opening the husk is a fairly sure test, try not to do this. Once you open an immature ear, it's susceptible to insect and bird attacks as it continues to ripen. It usually takes only a little practice to become a good judge by feeling the ends of the ears.
Sweetness is the key, so it helps to understand what makes corn sweet and why timing is so important in your harvest. The plant manufactures natural sugars when the kernels are filling out. These kernels are seeds that each contain a natural food-storage compartment as well as the corn embryo. A seed can't store sugars, but it can live on stored starches throughout the winter months and in its early stages of growth the following season. As soon as the kernels are full of sugar, the plant begins to convert it into starch. For best flavor, harvest the corn before this change can take place.
The sweetness of corn depends on the variety, temperature and amount of sunlight during the day when the ears are forming. The plant makes the most sugar on cool, sunny days. If the temperature is too hot, the sugar-making process is slowed. That's why the long, crisp, sunny days of early fall produce the sweetest corn.
Time It Right
If you have a choice, it's a good idea to harvest corn as close to the time you're going to eat or use it as possible. In fact, you might want to have the water boiling for corn on the cob before you head out to harvest.
To harvest sweet corn, grab an ear and twist it down and off the stalk.
If you want the sweetest corn possible, try to harvest each ear at its peak. Keep in mind that the natural conversion of sugar into starch is speeded up when you harvest. The moment you pick an ear of sweet corn, its sugars start to change into starches because the natural goal is to nourish seed for reproduction. In 24 hours, most varieties convert more than half their sugar content to starch. However, the new supersweet varieties stay sweet much longer after harvest than the old standards.
The loss of sugar is much slower at lower temperatures, so refrigerate corn if you're not going to be able to eat it right away. If you're not near a refrigerator and you have some harvested corn, keep the freshly picked ears in single layers, rather than stacking them. Corn tends to overheat inside its tight husks, so give each ear as much breathing room as possible. It also helps to cover the ears with a damp cloth.
Supersweet varieties have been developed to slow down the conversion of the natural sugars into starch, which makes these varieties last longer on the stalk, and helps them retain their flavor for a few days once harvested. Many seed catalogs claim that supersweet types are twice as sweet at harvesttime as ordinary hybrids, and four times as sweet after 48 hours.
Some people prefer corn that's less sweet, with more texture in each kernel. They take advantage of the natural conversion process and don't harvest corn until it's somewhat doughy from the increased starch content. They may also wait a day or two to serve it after picking.

If you want to store corn over the winter or grind your own cornmeal, give it time to harden completely. This means it has passed through its entire carbohydrate production cycle. It will then contain such heavy starch that it will be too hard to bite and it will keep for many months in storage.
Popcorn Pointers
The only way that growing popcorn differs from growing sweet corn is at harvesttime, and popcorn is actually easier to harvest because you don't have to catch it at the peak of sweetness. Leave popcorn in the garden until the stalks and husks are brown and dry, then twist and snap each ear from the stalk. Do this before the frost hits. To prepare popcorn for indoor curing, carefully strip away the dried husk from each ear. The kernels will be partially dried or "cured," a necessity for long-term storage.
Besides drying on the stalks, popcorn requires another four to six weeks of thorough drying in a warm, well-ventilated place. Corn can't pop unless there's the right amount of moisture inside the kernel. When it's heated, the moisture turns to steam, which causes the kernel to burst.
Place the ears in mesh bags or spread them out in an area where they'll have warm air circulating around them. You can also hang mesh bags full of popcorn ears in your garage for about four weeks. After curing, hang the bags of corn from the rafters of your root cellar. The corn can keep for years in the cool, dry, dark conditions there.
After a month of curing, the kernels can be taken off the ears and stored in airtight jars. Whether you're removing the kernels before storage or just before popping, there's no real trick to it. Simply grasp the ear firmly in both hands and twist until the kernels drop out. Once started, the kernels drop off with very little pressure. However, beware of the sharply pointed kernels if you're using your bare hands. After two or three ears, you may have a few nicks and scratches. If you want to remove the kernels from a lot of ears, it might be a good idea to wear gloves.
Popcorn doesn't take much garden space for a sizable harvest. Each ear is loaded with tiny kernels come harvesttime, and three or four five-foot-long rows should be plenty. Many popcorn varieties produce one or two ears per plant, so you may have enough by growing just five or six plants.
Pop homegrown popcorn just as you would store-bought. Heat a few tablespoons of oil in a deep pot. Sprinkle in enough kernels to coat the bottom and cover the pot. If not, as soon as you hear the first kernel pop, shake the covered pot vigorously while the rest pop. Shaking prevents the kernels from burning, and the unpopped kernels stay on the bottom nearest the heat. If you're using a popcorn popper, follow the manufacturer's instructions.
When the popping stops, remove the pot from the heat and take off the lid to let the steam escape. The popcorn is ready. Enjoy it plain, or add your favorite topping.