Moisture Needs

Sweet corn requires a continuous and adequate moisture supply for satisfactory growth and yield. In non-irrigated areas of the United States, sweet corn is grown with reasonable success where the rainfall from April through September is 20 inches or more and fairly well distributed. Unless the soil can retain a large supply Of water, sweet corn will suffer from lack of moisture if rainless periods last more than 2 weeks during the growing season.

In the South and Southwest, after the tassels show, the plants need rain or irrigation every week. For these areas, and where soil moisture is likely to be depleted, it is advisable to provide some supplemental irrigation. Furrow irrigation is satisfactory in most soils where runoff can be controlled.

Sweet corn varieties differ in the way their growth is affected by day length. Early maturing varieties developed for the North are not recommended for the South. They are adapted to the long, cool summer days in the North and do not make satisfactory growth in the deep South. Conversely the southern varieties are not adapted to the North. When planted in the North they may not silk and tassel until they reach 8 to 12 feet in height, and it is too late for them to produce edible corn before frost. Therefore, specific varieties are recommended for different sections of the country.

Hybrids

F1, hybrids have largely replaced the open-pollinated varieties. As with all hybrid plants, new seed must be obtained for each crop. Seed saved from the hybrid plants will not reproduce true to type and will not retain the hybrid vigor of the parent plants. Several public research agencies and private companies breed and introduce new varieties of sweet corn. As a result, a large number of excellent hybrids are available for gardeners. Some hybrids will be available for only a few years, being replaced by better ones.

Sweet corn variety trials are conducted each year by many State agricultural experiment stations, and lists of recommended varieties are published based on these trials. Contact your State agricultural extension service for a list of varieties recommended specifically for your area.

Sweet corn requires plenty of space and is adapted only to larger gardens exposed to full sunlight. It does best planted in rows 30 to 36 inches apart with single plants spaced 12 to 16 inches apart in the row. Overcrowding the corn will reduce the ear yield drastically. Planting four or more short rows is better than one long row to insure complete pollination. If the prevailing wind is across the row, pollen will be carried away from the silks and result in poorly filled ears.

To conserve space in the garden, corn may be planted next to vine crops, such as cucumber and cantaloupe. As the vines grow, they will grow between the corn plants.

Proper seedbed preparation is important for sweet corn in the garden since herbicides are generally not used. A clean freshly worked seedbed enables the seedling to emerge rapidly and get off to a good start ahead of grass and weeds. Seed should be planted to a depth of about 1 inch in moist, heavy soils and 1 to 2 inches in light, sandy soils, depending on the moisture conditions at planting time.

It is generally a good idea to plant at approximately twice the desired stand and thin to single stalks at the desired spacing after the seedlings have become well established. This will allow for any reduction in seed germination and for loss of a few emerging seedlings to insects, birds and other garden pests. About a quarter pound of seed is sufficient for each 100 feet of row.

Successive plantings are recommended in order to provide a steady supply of fresh corn throughout the practical harvest season. Also, an early, followed by a full season variety, may be planted at the same time to give a prolonged harvest period.

Once the desired stand has been established, the area should be kept free of weeds by cultivation and hoeing.

Diseases: Diseases are generally not a serious threat to clean, well nourished sweet corn plantings. Those that do occur most frequently are seedling root rot, Stewart's bacterial wilt, and common corn smut.

Root rot is caused by rot-producing fungi in the soil. It is often associated with a damp, cold soil, and may be evident as a slight stunting and irregular plant growth. Seed treatment with a fungicide provides good protection for the seedling during its early growth. Most sweet corn seeds packaged and sold commercially today have been treated with a fungicide. Use treated seeds whenever practical.

Stewart's wilt may appear at any stage of growth, but is most noticeable when plants attain considerable size. It produces yellow to brown streaks up to an inch wide on the leaves, and may extend the entire length of the leaf. Brown discoloration and sunken cavities form in the stalk near the soil line. Plants that become infected early may wilt and die. Those infected later may be only stunted and have streaked leaves.

The disease tends to be more prevalent after mild winters and is known to be spread by corn flea beetle. There are no sprays or seed treatments effective for controlling this disease.

Where wilt is suspected of becoming a problem, resistant varieties should be planted. Most varieties developed in recent years are resistant to the disease, particularly among the full season maturity group.

Common smut is characterized by the presence of large, fleshy galls on the stalks, leaves, tassel and ears. At first the galls are silvery white and spongy. Later, they turn brown or black, rupture and release large masses of powdery black spores. Smut galls are unsightly and render the affected ears inedible. Smut is promoted by injuries to the plant during cultivation, by insects, or hail. Again, there are no chemical treatments to control the disease.