Gardening Help FAQs

Here are answers to some of the most common questions we receive about garden plants. You will find concise information on general gardening techniques as well as plant selection and care. For detailed information on specific plant pests and problems refer to our Common Garden Pests and Problems page.

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Horticulture Questions and Answers

How do I grow sweet corn?

Sweet corn is classified according to its sugar content. The categories are standard varieties with about 20% sugar content, sugary enhancer hybrid varieties with about 25% sugar content, and shrunken (Sh2) gene or super sweet varieties with 40 to 50% sugar content. Sugary enhancer varieties are extra sweet and creamy. They are best eaten fresh and do not freeze well. Super sweet corn varieties hold their flavor longer than other varieties and are good for freezing. Their taste is very sweet. They must be isolated from varieties in the other two categories to prevent cross pollination in order to maintain this sweetness.

If you plant sweet corn of more than one category, stagger your plantings so they will mature at different times and not cross pollinate. Sweet corn also crosses readily with both field corn and popcorn if the plants are within 50 feet of each other and pollen is shed at the same time. Sweet corn pollinated by field corn will contain slightly less sugar and slightly more starch. It will not be as tender. Popcorn fertilized with field or sweet corn will dry more slowly but the eventual popping quality will be the same.

Sweet corn is an easy vegetable to grow but do not plant seeds until the soil is moderately warm and danger of frost has passed. In St. Louis, this is usually around May 1st. The soil must be 65 degrees before planting. The two sweeter corn varieties are particularly sensitive to cold soil. You can extend the harvest either by making several plantings of the same variety at 10 day intervals up to around August 1st for all season harvest or you can plant several varieties with different harvest dates all at the same time. Sweet corn produces best if single plants are at least 10 inches apart in the row. They will need 30 to 36 inches between rows.

Make sure you plant several rows of each individual variety side by side at each seeding to ensure good pollination. Sweet corn is a heavy feeder, especially of nitrogen. Fertilize plants with a side dressing of nitrogen about the time the tassels and silks appear. Water regularly. Harvest when the ears are full size and the silks have browned and dried.

Pull sweet corn plants as soon as you harvest the last ear. Chop the stalk while it is still green and succulent and add it to the compost pile.