Edible of the Month - Sweet Corn

By National Gardening Association Editors

Nothing beats the taste of freshly harvested sweet corn from the garden.

There are few vegetables that say "summer" like sweet corn. The sweet taste and tender texture of freshly harvested corn is a mainstay at summer picnics and barbecues. Corn is native to the Americas and was originally used for making flour, meal, and drinks. Sweet corn was actually a mutation of the more common dent and flour corns and wasn't prized or intentionally grown by native peoples, with the exception of some eastern North American tribes. However, it was sweet corn that Europeans loved when they came to America and its popularity has spread ever since.

Sweet corn took a major step forward in sweetness with the advent of modern hybridizing. Corn ears became larger and sweeter and plants more productive. Now many varieties are so sweet you can literally eat them off the stalk, without cooking, if you're so inclined. Sweet corn has the reputation of losing its sweetness quickly after harvest. Many a gardener would rush home with the day's picking to cook before it became starchy (usually within hours of harvest). However, newer supersweet varieties have genes that keep the corn sweeter longer, eliminating the need to cook it immediately.

While traditional flour and cooking corn varieties come with kernel colors ranging from white to blue (think of blue tortilla chips), sweet corn varieties have mostly yellow, white, or bi-colored kernels. However, there are red sweet corn and black sweet corn varieties available, too. Not only is sweet corn a tasty summer treat, it's loaded with protein and vitamins such as lutein (for good vision) and folate (B-vitamin), so it's a healthy addition to any meal.


Sweet corn is a heat-loving crop and needs warm soils to germinate and grow well. It grows quickly in summer, reaching 4 to 8 feet tall depending on the variety. Some farmers say on a hot summer day they can almost hear the corn grow. When growing sweet corn in a home garden, it's important to select early, mid, and late season varieties to extend the harvest season and prevent cross pollination.

Harvest sweet corn when the silks on the ears have turned dark brown and the ear is firm when squeezed.

There are some terms to know as well. While there are some open pollinated, heirloom sweet corn varieties on the market, hybrids dominate. Of the hybrids, there are generally three types.

Standard Sugary – The traditional hybrid varieties, such as 'Silver Queen', that have a sweet and "corny" taste, but don't hold their sweetness long on the cob after harvest.

Sugar-enhanced (se) – This hybrid has a special gene that enhances the sweetness and tenderness of the kernels.

Supersweet (sh2) – This hybrid goes a step beyond sugar-enhanced, with even sweeter ears that can be stored in the refrigerator for up to 1 week without losing their sweetness. Some folks think they actually are too sweet and have lost their "real corn" flavor. These varieties are more finicky to grow as far as soil temperature and fertility requirements.

Here are some of the best varieties to try in your garden. Days to maturity are listed after the variety and are from seeding.

'Black Aztec' (80 days) – This heirloom Southwest variety is drought tolerant. The kernels turn black when mature.

'Country Gentlemen' (90 days) – An 8-foot tall heirloom, with white, creamy-textured kernels.

'Early Sunglow' (63 days) – This standard hybrid, small-space variety has 4-foot tall stalks that produce yellow ears.

'Honey N' Pearl' (76 days) – An early, long-eared (9 inches), bicolor, supersweet variety with a tight husk that resists corn earworm insects.

'How Sweet It Is' (87 days) – A very sweet, white, supersweet variety with large (8 to 9 inches long) ears and tender kernels.

Side shoots from the bottom of the corn stalk called tillers should be left growing because they help anchor the corn stalk.

'Quickie' (68 days) – A sugar-enhanced bicolor variety that's tolerant of cool soils.

'Ruby Queen' (75 days) – A new sugar-enhanced variety with unique ruby red kernels that hold their color even when cooked.

'Silver Queen' (92 days) – This standard hybrid has 8-inch long white ears and is considered one of the best tasting corn varieties.

'Sugar Buns' (72 days) – This yellow, sugar-enhanced variety has 5- to 7-inch long ears with a creamy texture.


Sweet corn, especially supersweet varieties, grows best in warm, well drained soils. Wait until soil temperatures are in the 60Fs before planting. Sweet corn is in the grass family and likes fertility — especially nitrogen. Amend the soil with a 3-inch thick layer of compost before planting. Consider planting corn where legumes, such as beans, or cover crops, such as clover, were planted before to utilize the nitrogen they produced. In small gardens consider growing sweet corn in clumps with pole beans and squash to recreate a traditional Three Sisters Garden


Plant sweet corn seed in tilled soil two weeks after your last frost date. The best way to plant sweet corn in a home garden is in blocks. Short blocks increase the pollination of the ears and produce better quality corn. Plant blocks of all one variety so they don't cross pollinate each other. Corn is wind pollinated and if the pollen from one variety falls on another ear, you'll get a mix of colors and textures in that ear. Blocks also help keep the corn from blowing over in a wind storm.

Plant at least four rows about 10 to 20 feet long spaced 2 feet apart. Leave a 2- to 4-foot wide walkway for harvesting between blocks. Plant seeds 6 inches apart, 1- to 2-inches deep. After germination, thin to 12 inches apart.

Some varieties may be treated with a fungicide (often the seed is brightly colored) to prevent rotting while germinating. Avoid this type of seed if you're an organic gardener. Otherwise, be sure to wear gloves when planting and wash up well after working in the garden.


Raccoons almost have a 6th sense when it comes to knowing when your corn is ripe. Protect plants with an electric fence.

Once it has germinated, corn grows fast. When 8 -inches tall, hill the rows by mounding soil up around the plants to prevent the corn from lodging or falling over during summer storms. Fertilize with an organic 5-5-5 fertilizer when corn is knee high and again when the silks (fine hairs on the ears) form. Yellow corn leaves is a sign of too little nitrogen fertilizer. Dark green leaves are a sign of too much nitrogen fertilizer. Keep plants well watered. Thin, curled, "pineapple" leaves is a sign of water stress. Water deeply to 6 inches, especially during pollination and ear filling times.

Sweet corn is attacked by many insects and diseases. Insects such as corn earworm, corn borer, Japanese beetle, and corn rootworm can reduce your harvest. Control them with the appropriate sprays. To control diseases such as corn leaf blight, choose resistant varieties, rotate crops, and clean the garden well in fall.

Raccoons love sweet corn and seem to know exactly when it's ripe. They often attack the night before you're ready to harvest! Protect small plantings by wrapping individual ears in a paper bag attached to the stalk with duct tape or stringing an electric fence around the garden.


Sweet corn plants usually produce 1 to 2 good sized ears per stalk. The ears are ready to harvest about 20 days after the first silks appear. When squeezed, the ears will feel filled. When mature, if you pull back the husk near the tip and pinch an individual kernel, it should squirt out a milky liquid. Immature ears squirt a watery liquid, while over mature ears have tough and doughy kernels. Harvest mature ears by pulling down with a sharp motion without breaking the stalk. Check for ripe corn every few days once you start harvesting.

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