Corn

corn field

Sweet corn is a popular summer vegetable but requires a significant space investment to have a good yield. Sweet corn does not adapt well to small garden areas because closely spaced plants will produce only 1 to 2 ears. Sweet corn is also wind-pollinated, and different varieties can easily cross in small spaces and impact the quality of ears. Types of sweet corn are categorized based on their genetic types.

Normal sugary (su types). This is the oldest, traditional type of sweet corn. It is tender and creamy but will quickly become starchy. These varieties must be isolated from sh2 and sy types.
Sugary enhanced and Triplesweet (se types). These types have an increased sugar level and even more tender kernels. The sugar turns to starch more slowly than su types. These varieties must be isolated from sh2 types.
Supersweet (sh2 types). Supersweet varieties have up to 50% more sugar than regular sugary types. They have a crisp, crunchy texture to the kernels and will keep their sweetness for a week in the refrigerator. The shriveled seeds do not germinate well in cold soil. This variety must be isolated from other sweet corn types.
Synergistic (sy types). Synergistic types of sweet corn have a combination of the above genes. They have at least one se gene and may have a combination of sh2 or su or both. They combine the beneficial traits of all the other genes to have improved sweetness, texture, and storage life. Isolation requirements must be determined for each variety, or plan to isolate from all other types.
Augmented supersweet (sh2 with some se characteristics). This type of corn is a supersweet that also has the se trait in the kernels, resulting in a corn with high sugar, tender texture, and good storage life.

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How to Grow

Many new hybrid varieties of sweet corn are available in all of the genetic categories previously discussed. The colors range from yellow to white to bicolor, yellow and white kernels together on the same ear. Early varieties that require 65 to 75 days to mature produce smaller stalks and ears, while later varieties requiring 75 days or longer produce larger plants and larger ears. Varieties are available with resistance to several common diseases such as maize dwarf mosaic, smut, and bacterial wilt. For early season planting, choose a type that is adapted to cold soils.

Plants should be 8 to 12 inches apart in rows at least 3 feet apart. Do not crowd plantings, as weak, spindly, unproductive plants will result. Plant the kernels an inch deep. If many seeds fail to germinate, do not attempt to replace missing plants; replant the entire planting. Plant corn in blocks of at least four rows to ensure adequate pollination.

Sunlight: Sweet corn needs full sun and at least 8 hours of direct light during the day.
Temperature: Sweet corn is a warm-season crop and should be planted in mid- to late April. The sh2 varieties and other newer varieties that have a smaller, more shriveled seed will rot in cold soil; do not plant these types until early May. Soil temperature should be at least 60°F when planting corn seed. To have an earlier harvest, sweet corn seeds can be sown as double rows (14 to 24 inches apart) under clear, perforated plastic (1 to 1.25 mil). The plastic is left on the plants for about 30 days and then is slit and removed when plants are 6 to 12 inches in height.
Watering: Sweet corn needs regular watering as well because its sparse, inefficient root system does not reach to deep soil water. Apply 1 to 1½ inches of water per week.
Soil and Fertilization: Sweet corn is a member of the grass family and needs considerably more nitrogen fertilizer than other garden plants. A side dressing of additional fertilizer sprinkled along the row every several weeks is important.
Pests and Diseases: Sweet corn pollinates poorly in 100-degree weather, and ears with missing kernels or gaps may result. Control weeds when sweet corn is small to reduce competition. Corn earworm is a common insect pest of sweet corn. Mineral oil mixed with a Bt insecticide (Dipel®) can be effective for controlling corn earworm. The oil is applied to the tip of the ear by hand on each silk about two days after the silk emerges from the ear. This is a time consuming method of treatment. Raccoons and deer can also be major pests of sweet corn. Electric fencing is the best option to keep them out of your garden. More information on control of raccoons can be found in this news article.
Succession Planting: Successive plantings of corn are important to spread the harvest over a longer period. Make additional plantings when the previous planting is ½ to ¾ inch tall.

Harvest and Storage

sweet corn ear Sweet corn is ready for harvest when the juice in the kernel appears milky as you puncture a kernel with your finger. The ear should be well filled to the tip. This ideal harvest stage lasts for only a few days in hot weather, and regular checking for maturity is important. The silks of mature ears are generally completely dry and brown. Twist and pull the ear from the plant by bending the ear down sharply. Use corn immediately or store it in a cold place immediately after harvest. Pick corn early in the morning when it is cool outside. Store corn for only a few days in a refrigerator before using. Corn is easily frozen for later use.

For information on preserving sweet corn check out this Preserve it Safe, Preserve it Fresh publication.

Recipes

Sweet corn on is a summer staple for many individuals. Corn is an excellent source of thiamin and a good source of fiber, vitamin C, folate, niacin, phosphorus, and manganese. Corn is low in sodium and fat.

Fresh Corn Salsa

Ingredients	Directions
4 ears fresh corn, kernels removed 1 cup green bell pepper, chopped ½ cup red onion, chopped 2 tomatoes, chopped 2 garlic cloves, chopped 2 Tbs lemon juice or vinegar ½ tsp black pepper ¼ tsp salt	Prepare ingredients as directed in the ingredient list. Combine all ingredients in a large bowl. Refrigerate for at least one hour before serving.

Recipe source: North Dakota State University Extension

Corn and Green Chili Salad

Ingredients	Directions
2 cups corn ( fresh or frozen and thawed) 1 can diced tomatoes with green chilies (10 ounce) ½ Tbs vegetable oil 1 Tbs lime juice ⅓ cup green onion (sliced) 2 Tbs cilantro (fresh chopped)	Combine all ingredients in a medium bowl. Mix well.

Recipe source: University of Missouri Extension

Watermelon, Black Bean, and Corn Salsa

Ingredients

Directions

1 can corn kernels, rinsed and drained
1 can black beans, rinsed and drained
½ medium purple or white onion, coarsely chopped
1 to 2 jalapeno peppers, chopped
1 clove garlic, minced
1 tsp ground cumin
1 tsp chili powder
2 Tbs salad oil (such as canola or olive)
1 lime, juiced
1 ½ cups watermelon, chopped (with seeds removed)
Optional:
- Fresh cilantro, chopped
- Cucumbers, diced
- Avocado, diced

Mix all ingredients except watermelon.
Gently fold in watermelon and chill.
Serve with baked chips or as a side dish with grilled meat, poultry or fish.

Recipe source: North Dakota State University Extension