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Sweet Corn - Zea mays

Including: popcorn, ornamental, miniature corn


Zones 3 and warmer. Use only short-season cultivars in coldest areas

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Full sun

Rich, well-drained loam; pH 5.5 to 6.8

Keep soil evenly moist, but not wet

Plant 7 to 15 inches (18 to 38 cm) apart in rows 30 to 40 inches (75 to 100 cm) apart


Harvest corn when the silks have turned brown and dry, and the ear feels full. Check by pressing a thumbnail into a kernel, it should have milky liquid come out. If the liquid is clear, it's too early, if no liquid at all, it's too late

Comments: Most sweet corn comes in white, yellow, or bicolored (both yellow and white), and it is divided into three major groups: standard, sugar-enhanced, and super sweet. Standard cultivars do not have any of the special genes that make modern corn taste so sweet, but they are still very popular with home gardeners (Standard hybrids such as 'Silver Queen') that want that traditional sweet corn flavor. Sugar enhanced corn varieties are sweeter and more tender than standard types, while super-sweet varieties stay sugary for days after harvesting. Keep in mind, when choosing corn cultivars for your garden, that super-sweet varieties can cross-pollinate with other non-super-sweet types, which can result in starchy, tough, kernels. Make sure to separate unlike varieties by planting at different times (plant 10 days earlier or later than the other), therefore they will be pollinating at different times, or you can space the blocks of corn a minimum of 25 feet (7.5 m) apart. More space apart would be ideal, but only if you have the space.

Planting Site: Corn is pretty tolerant of many soil textures, but it prefers deep, well-composted soil with high organic matter. If your soil drains poorly, plant your crop in raised beds. If you live in a cooler climate, prepare your rows and then cover them with black plastic for two to four weeks, in sunny weather, before planting to help warm the soil for early crops. When you are ready to sow the seeds, remove the plastic. Choose a site that has some wind, because corn needs wind for pollination.

Corn Planting & Growing Guidelines: Look for varieties to suit the length of your growing season. For example, early maturing cultivars are ideal for areas that have cold, damp springs. Dwarf cultivars produce 4 to 5 inch (10 to 12.5 cm) ears and are ideal for small gardens.

Sow seeds after the last spring frost, or one to two weeks earlier if you used the tip above and and warmed the soil first by covering it with black plastic for a week or more in sunny weather. Corn seed germinates poorly in cold, wet soil and may rot. Direct sow seeds 1 to 2 inches (2.5 to 5 cm) deep, placing three seeds every 7 to 15 inches (18 to 38 cm) apart, in rows 30 to 40 inches (75 to 100 cm) apart, in blocks of a minimum of four rows. Planting in blocks promotes even pollination which is critical for full, well-filled ears. Corn seed normally germinates quickly, in seven to ten days. Corn grows quickly and needs regular fertilizer and water.

If you have the room, you can plant successive crops every 10 to 14 days through midsummer, or until about 90 days before the first fall frost. Choose an early-maturing cultivar for the last planting.

Keep the soil evenly moist, but not wet. Never allow young plants to dry out, and supply regular water when tassels begin to appear. Always water plants from below; water sprayed over the plants can wash the pollen away. Control weeds and help conserve moisture by mulching.

Hilling is very important for corn because corn is a heavy feeder and needs extra nutrition as it grows, and hilling helps anchor the plant, making the stalk more rigid. A sturdier stalk helps when the plant is loaded with developing ears, and it helps it withstand wind. You will need to hill corn twice during its lifetime:

1. When the corn is 6 to 8 inches (15 to 20 cm) tall
2. When the corn is about 1 foot (30 cm) tall

If you need to see how this is done, read our article: How To Maintain A Vegetable Garden

To hill, we carefully take soil from the pathway between the rows (don't dig too closely to the corn plant, you can damage roots) and pull it up to the base of the corn plant.

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    Fertilizing: Lightly broadcast some 10-10-10 over the area, till in, and then plant transplants or sow seeds. Side dress (fertilize) the corn twice during its lifetime:
    1. When the corn reaches 6 to 8 inches (15 t o 20 cm) tall
    2. When the corn starts to tassel. Simply take some balanced fertilizer - like 5-5-5 or a 10-10-10 complete fertilizer - although you can also use hydrolyzed fish or other balanced fertilizer, and lightly sprinkle it along one or both sides of the stalks. A good time to do this is the same time you hill your corn. Side dress with the fertilizer, then hill over the fertilizer and water in.

    Pest and Disease Prevention: To prevent disease problems choose cultivars that tolerate or resist common corn diseases. Rotate corn with other crops to prevent recurring pest and disease problems. If you've had problems ins the past, you can apply parasitic nematodes to the soil before planting to keep wireworms, seedcorn beetles, and other soil-dwelling pests in check. To help control earworms drop mineral oil into immature ears as soon as you see the pest.

    Common Problems:

    1. Corn Earworm
      See our article on this insect and ways to get rid of it: Corn Earworm

    2. Patchy or unevenly filled out ears
      Lack of pollination is responsible if ears of corn don't fill out all the way, or only about half the cob is covered with kernels, or you see patchy spots.

      Rain and wind can affect good pollination - wind can blow the pollen away very easily, and rain can stick the silks together so that some of them do not get pollinated.

      Hand pollination solves the problem and it's easy to do. Choose a morning when the wind is calm. Look for plants whose tassels are just beginning to shed pollen. Shake the tassels gently into a paper bag, then sprinkle the collected pollen onto the greenish silks of all the developing ears of corn. Repeat this process once or twice over the next few days.
    Days to Maturity: 55 to 90 frost free days after planting depending upon the cultivar.

    Harvest and Storage: Harvest corn when the silks have turned brown and dry, and the ear feels full. Check by pressing a thumbnail into a kernel, it should have milky liquid come out. If the liquid is clear, it's too early, if no liquid at all, it's too late. Corn tastes best when picked in the late afternoon. Harvest by holding the stalk firmly, and then twisting the ear off of the plant in a downward direction. Because the sugar in the corn turns to starch very quickly, eat or preserve corn immediately after harvesting.

    Special Tips: In gardens where space is limited, interplant a fast-growing crop like lettuce between the rows of corn. The lettuce is harvested before the corn casts too much shade.

    The sweet corn growing information above applies to the following:

    Miniature Corn (Zea mays var. rugosa) - Also called baby corn. Pick tiny ears a day or two after the silks appear and use whole in stir fries or for pickling.

    Ornamental Corn (Zea mays var. indurata) - Also called Indian corn. This colorful field corn comes with kernels of many colors and hues. Many varieties are excellent for grinding into a cornmeal or flour. Harvest the corn when the kernels cannot be penetrated with a thumbnail, then pull back to husks and hang to finish drying.

    Popcorn (Zea mays var. praecox) - These ears of corn have very dense kernels that pop when heated. Harvest as dry as possible, pull back the husks and hang in an airy place to cure. Test pop a few kernels to determine when the corn is dry enough to be shucked and stores in bags or jars.

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