SWEET CORN

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Compliments of Urban Extension, Illinois

Sweet corn is a warm-season vegetable that can be grown easily in any garden with sufficient light, fertility, growing season and space. It is especially popular with home gardeners because it tastes appreciably better when it is harvested and eaten fresh from the garden. Successive plantings can yield continual harvests from early summer until frost if the weather cooperates.
Sweet corn may be divided into three distinct types according to genetic background: normal sugary (SU), sugary enhancer (SE) and supersweet (Sh2).
Standard sweet corn varieties contain a "sugary (SU) gene" that is responsible for the sweetness and creamy texture of the kernels. SUs are best suited to being picked, husked and eaten within a very short time. In the home garden, this is sometimes possible but not always practical. The old adage was "start the water boiling, run to the patch, pick and husk the corn, run back to the pot, cook the corn, and eat or process immediately."
Sugary enhancer hybrids contain the sugary enhancer (SE) gene, that significantly raises the sugar content above standard SUs while retaining the tenderness and creamy texture of standard varieties. The taste, tenderness and texture are outstanding. SEs are the gourmet corns of choice for home gardeners because they contain the best qualities of both SU and Sh2 types. Fresh from the garden, virtually all current SE releases have eating quality that is superior to all other types. No isolation from standard SUs is necessary.
Supersweet hybrids contain the shrunken -2 gene and have a higher sugar content than the standard SU varieties. The kernels of the extra-sweet varieties have a crispy, tough-skinned texture and contain low amounts of the water-soluble polysaccharides that impart the creamy texture and "corny" flavor to other sweet corn varieties. Although the lack of creamy texture is not especially noticeable in fresh corn on the cob, it affects the quality of frozen and canned corn, as does the toughness of the seed coat. Unless corn must be stored, shipped or mechanically harvested, SEs are superior in eating quality to Sh2s.
Supersweets (Sh2) should be isolated from any other type of corn tasseling at the same time to ensure sweetness and tenderness. Their pollen is weak and easily supplanted by other types, which causes the kernel to revert to a form with the toughness and starchiness of field corn. Because corn is wind-pollinated, this isolation distance can be 500 feet or more, especially downwind.

Recommended Varieties

Most of the varieties listed here (like nearly all sweet corn sold today) are hybrids. They are arranged by genetic type and kernel color. The maturity dates are relative because the actual number of days to harvest varies from year to year and location to location.
Standard (SU)

Yellow	Harvest	Ear Size	Comments
Earlivee	58 days	7"-14 rows	extra early
Golden Cross Bantam	85 days	8"-12 to 14 rows	old home-garden variety
Iochief	86 days	8"-14 to 16 rows	popular midseason variety
Jubilee	82 days	8"-16 rows	high yield; deep, narrow kernels; excellent for canning I tried this jubilee last year 2012 and did not like the quality, maybe it need more water as we had a drought.
NK-199	84 days	8"-18 to 20 rows	extremely thick, attractive ears; silks easily removed
Seneca Horizon	65 days	7"-16 to 18 rows	excellent quality
Sundance	69 days	1/2"-14 rows	best cold-soil tolerance, early season vigor; handsome ears

White	Harvest	Ear Size	Comments
Pearl White	75 days	7 to 8"-12 to 16 rows	good cool-soil and drought tolerance; easy snapping
Platinum Lady	86 days	8 1/2"-14 rows	delicate flavor; tender kernels; slender, elegant ears
Silver Queen	92 days	8 to 9"-14 to 16 rows	dark green flag leaves, attractive ears; standard, high-quality white corn; resistant to bacterial wilt and Helminthosporium

Bicolor	Harvest	Ear Size	Comments
BiQueen	92 days	8 to 9"-16 rows	like a bicolor Silver Queen
Butter & Sugar	75 days	7"-14 rows	popular for home garden
Honey & Cream	80 days	7"-12 to 14 rows	sweet, tender; long, tight husks
Quickie	64 days	7 1/2"-12 rows	earliest SU bicolor
Sugar & Gold	67 days	6 1/2"-10 to 12 rows	husk green, with reddish tinge; excellent quality; prefers cooler-season areas

Sugary Extender (SE)

	Harvest	Ear Size	Comments
Bodacious	72 days	8"-16 to 18 rows	superior flavor, holding ability; ears snap easily; prefers warm soil
Champ	68 days	8"-16 to 18 rows	excellent eating quality, tip cover
Incredible	83 days	8 to 9"-18 rows	big, flavorful ears; excellent appearance, yield
Kandy Korn	89 days	8"-14 to 16 rows	purplish red-streaked ear flags, excellent quality, long shelf life
Maple Sweet	70 days	7 1/2"-14 to 16 rows	excellent flavor, easy snapping
Merlin	84 days	9"-20 to 22 rows	superior flavor, ear size, disease tolerance; easy snapping
Miracle	84 days	9 1/2"-16 to 18 rows	good holding quality; large, tender, attractive, tasty ears
Precocious	66 days	7"-12 to 14 rows	very early; excellent eating, good tipfill
Spring Treat	67 days	7"-14 rows	easy snapping, straight rows of kernels
Sugar Buns	72 days	7 1/2"-14 rows	excellent flavor; attractive, relatively small ears; deep kernels
Terminator	83 days	9"-20 rows	large ears, superior disease resistance
Tuxedo	75 days	7 1/2"-16 to 20 rows	excellent early vigor; good tipfill, husk cover; excellent eating quality; tolerant to Stewart’s wilt, and smut

White	Harvest	Ear Size	Comments
Alpine	79 days	8"-16 rows	widely adapted; excellent yield; cool-soil tolerance; attractive ear
Argent	86 days	8 to 9"-16 rows	good cold-soil vigor; tolerant to Stewart’s wilt; like a white Incredible
Avalanche	78 days	8"-16 rows	excellent eating; good ear appearance
Cotton Candy	72 days	7 to 8"-16 to 18	extended harvest; reddish green stalks
Divinity	78 days	8"-16 rows	excellent flavor, tenderness; snow white color; excellent tip cover; tolerant to drought, Stewart’s wilt
Pristine	76 days	8 to 9"-16 rows	terrific eating quality, tolerant to Stewart’s wilt
Seneca Starshine	71 days	7 to 8"-16 rows	blocky ears, with pure white kernels; excellent tenderness, flavor, appearance; prefers 50°F or higher soil temperature for germination
Seneca White Knight	74 days	8 to 9"-16 rows	high quality; attractive ears; great taste
Snowbelle	79 days	7 to 8"-14 to 16 rows	creamy texture; pretty, compact ears
Spring Snow	65 days	7 to 8"-12 rows	excellent husk cover; very early; attractive ears; very tender kernels; compact plant
Sugar Snow	71 days	8 to 9"-16 rows	extremely sweet, snow white kernels; good cold-soil tolerance
Telstar	79 days	8"-16 rows	vigorous; dark green flag leaves; tasty; attractive ear
Ambrosia	75 days	8"-16 rows	good spring vigor; fairly large, tasty ears; tolerant to Stewart’s wilt
Calico Belle	79 days	8"-16 to 18 rows	high yield; attractive; delicious taste; good disease tolerance
D’Artagnan	71 days	8"-16 rows	superior quality in an early SE bicolor
Diamonds & Gold	79 days	8"-18 rows	sweet, tender; good tipfill; attractive dark green ears
Double Delight	85 days	9"-16 rows	large, tasty ears; dark green husk; like a bicolor Incredible
Double Gem	74 days	8 to 9"-16 to 18 rows	excellent eating quality; blocky ears; usually double ears on stalks
Kiss ‘N Tell	68 days	7 to 8"-14 to 16 rows	two ears per stalk; good tipfill
Lancelot	80 days	8"-16 to 18 rows	vigorous, stress-tolerant plant; good yields; high quality ears under adverse conditions
Medley	73 days	8"-16 rows	dark green flags; good tip cover; tolerant to Stewart’s wilt
Peaches & Cream	83 days	8"-16 to 18 rows	tasty, poplar home-garden variety; vigorous plant; good ear protection
Seneca Brave	73 days	8"-18 to 20 rows	husky, excellent quality ears; strong plants
Seneca Dawn	69 days	7 to 8"-14 to 16 rows	excellent early bicolor; good vigor, eating quality

Supersweet (Sh2)

Yellow	Harvest	Ear Size	Comments
ChallengerCrisp ‘N Sweet	85 days	9"-18 rows	high yield; excellent disease resistance; good germination, seedling vigor
Early Xtra Sweet	70 days	8"-16 rows	like the original, but earlier
Excel	82 days	8 1/2" - 16 rows	exceptionally high yield, easy to harvest
Illini Gold	79 days	8 1/2"-16 rows	midseason supersweet
Illini Xtra Sweet	85 days	8"-14 to 16 rows	the original SH2 supersweet hybrid
Jubilee Supersweet	83 days	9"-18 rows	excellent home garden supersweet
Showcase	83 days	8"	large ear on short plant, outstanding eating quality

White	Harvest	Ear Size	Comments
Aspen	83 days	8 to 9"-16 rows	large, attractive ears; high eating quality
Camelot	86 days	8"-18 to 20 rows	clean, sturdy plants; excellent quality, holding traits
How Sweet It Is	85 days	8"-16 rows	All-America Selection winner, sensitive to cold soil, holds quality well
Pegasus	85 days	8 1/2"-18 rows	good cold soil germination, vigor
Treasure	83 days	8 1/2"-18 rows	good vigor, seedling emergence

Bicolor	Harvest	Ear size	Comments
Aloha	82 days	9"-16 rows	excellent appearance
Dazzle	82 days	8"-16 to 18 rows	good looking ear; good disease resistance; creamy texture
Honey ‘N Pearl	78 days	8 1/2"-16 rows	1988 All-America Selection winner, stands well, excellent quality
Hudson	83 days	8"-18 rows	smooth, well-filled ears; superior eating quality, tenderness
Phenomenal	85 days	8 1/2"-16 rows	excellent eating quality, beautiful ears
Radiance	73 days	8"-16 to 18 rows	excellent seedling emergence, plant vigor

When to Plant

Sweet corn requires warm soil for germination (above 55°F for standard sweet corn varieties and about 65°F for supersweet varieties). Early plantings of standard sweet corn should be made at, or just before, the mean frost-free date unless you use special soil-warming protection such as clear polyethylene mulch film.
For a continuous supply of sweet corn throughout the summer, plant an early variety, a second early variety and a main-crop variety in the first planting. For example, you may wish to select Sundance (69 days) for the first early variety, Tuxedo (75 days) for the second early variety and Incredible (83 days) for the main-crop variety. Make a second planting and successive plantings of your favorite main-crop or late variety when three to four leaves have appeared on the seedlings in the previous planting. Plantings can be made as late as the first week of July.
Open-Pollinated (SU)

Yellow	Harvest	Ear size	Comments
Ashworth	69 days	6 to 7" ears, 12 rows	good cold soil germination; good flavor for an early type
Golden Bantam	82 days	6 to 7"ears, 10 to 14 rows	rich corn flavor, sweet, tender

White	Harvest	Ear size	Comments
Country Gentleman	96 days	7" ears, kernels not in rows	very tender, shoe-peg type; drought resistant
Stowell’s Evergreen	100 days	9"ears, 18 to 20 rows	big, juicy, white kernels; ripen over long period
Trucker’s Favorite	95 days	8 to 9" ears, 14 rows	delicious white kernels, high yields

Bicolor	Harvest	Ear size	Comments
Double Standard	73 days	7"ears, 12 to 14 rows	first bicolor open-pollinated type; good cold soil germination good flavor, tenderness; traditional corn taste

Black	Harvest	Ear size	Comments
Black Aztec	75 days	7"ears, 8 to 10 rows	vigorous drought tolerant; sweet white kernels in roasting ear stage, dark blue-black at maturity; good for blue corn meal

Spacing & Depth

Plant the kernels (seeds) 1/2 inch deep in cool, moist soils and 1 to 1 1/2 inches deep in warm, dry soils. Space the kernels 9 to 12 inches apart in the row. Plant two or more rows of each variety side by side to ensure good pollination and ear development. Allow 30 to 36 inches between rows.
All sweet corns should be protected from possible cross-pollination by other types of corn (field, pop or flint). If you plant supersweet or synergistic sweet corn varieties, plan your garden arrangement and planting schedule so as to prevent cross-pollination between these varieties and with any other corn, including nonSh2 sweet corns. Supersweet varieties pollinated by standard sweet corn, popcorn or field corn do not develop a high sugar content and are starchy. Cross-pollination between yellow and white sweet corn varieties of the same type affects only the appearance of the white corn, not the eating quality.

Care

Cultivate shallowly to control weeds. Chemical herbicides are not recommended for home gardens. Although corn is a warm-weather crop, lack of water at critical periods can seriously reduce quality and yield. If rainfall is deficient, irrigate thoroughly during emergence of the tassels, silking and maturation of the ears.
Hot, droughty conditions during pollination result in missing kernels, small ears and poor development of the tips of the ears. Side-dress nitrogen fertilizer when the plants are 12 to 18 inches tall.
Some sweet corn varieties produce more side shoots or "suckers" than others. Removing these side shoots is time consuming and does not improve yields.

Harvesting

Each cornstalk should produce at least one large ear. Under good growing conditions (correct spacing; freedom from weeds, insects and disease; and adequate moisture and fertility), many varieties produce a second ear. This second ear is usually smaller and develops later than the first ear.
Sweet corn ears should be picked during the "milk stage" when the kernels are fully formed but not fully mature. This stage occurs about 20 days after the appearance of the first silk strands. The kernels are smooth and plump and the juice in the kernel appears milky when punctured with a thumbnail. Sweet corn remains in the milk stage less than a week. As harvest time approaches, check frequently to make sure that the kernels do not become too mature and doughy. Other signs that indicate when the corn is ready for harvest are drying and browning of the silks, fullness of the tip kernels and firmness of the unhusked ears.
To harvest, snap off the ears by hand with a quick, firm, downward push, twist and pull. The ears should be eaten, processed or refrigerated as soon as possible. At summer temperatures, the sugar in sweet corn quickly decreases and the starch increases.
Cut or pull out the cornstalks immediately after harvest and put them in a compost pile. Cut the stalks in one foot lengths or shred them to hasten decay.

Common Problems

Corn earworms are a problem in sweet corn every year. Earlier plantings are not badly infested in areas where the pest does not overwinter, but later harvests usually have severe earworm damage unless timely control measures are followed. Corn earworms deposit eggs on the developing silks or on the leaves near the ear. The tiny caterpillars follow the silks down into the ear, where they feed on the tip. Only one corn earworm will be found per ear because the caterpillars are cannibalistic, with the largest devouring any others present. Once the worm is inside the protective husk covering, there is no effective control. Anything that restricts the worm-such as tightening the tip of the husk with a rubber band or clothespin after the silk appears, or inserting mineral oil (1/2 medicine dropperful) in the silk tube-helps to decrease the damage.
Corn rootworm beetles may cause extensive silk damage that interferes with pollination. Later plantings usually suffer the greatest damage, especially where field corn is grown. Beetles multiply in early plantings of field corn, mature and migrate to plantings of young, tender sweet corn. Silk and the young, tender, green leaves are preferred feeding sites. If infestation is sufficient to remove silk before pollination, cobs develop without a full set of kernels. Control measures must be taken as the silk emerges.
European corn borers damage stalks, tassels and ears. As their name indicates, corn borers bore into the plant; and the stalks break over when damage is severe. Corn borers also may bore into the cob and be found after cooking. A suggested insecticide can be applied at 5 day intervals, beginning when eggs hatch in June. Spray applications for earworms usually give adequate control of corn borers.
Flea beetles often attack early in the spring as the corn plants emerge through the soil. Flea beetles can be quite damaging when numerous and they may carry Stewart's bacterial wilt disease.
Stewart's wilt is a bacterial disease spread by the flea beetle. This disease causes yellow streaks in the leaves, stunting and death of young plants of susceptible varieties. The disease occurs more frequently in the southern states and is not severe after cold winters or when resistant varieties are planted. If possible, plant varieties with good resistance.
Smut is caused by a fungus that invades the kernels. It develops as a swollen black pustule (gall) in the ear and sometimes infects the tassel. Some sweet corn varieties are more tolerant to smut than others. Smut occurs most frequently on white varieties and is often severe when extremely dry or hot weather occurs just before and during tasseling. Remove and destroy smut galls while they are moist and firm. Do not discard these galls in or near the garden. Place in the garbage or burn them. The smut is not poisonous, but it is unpleasant to handle. Break off the infected part of the ear. The remainder is suitable for eating.
The immature smut fungus or "maize mushroom" is highly prized in Mexican cooking. Harvest when the fungus is expanded, but before it becomes black and dried out. The time generally is about 2 to 3 days before the sweet corn reaches peak eating quality.

Questions & Answers

Q. How long does it take sweet corn to develop from the first appearance of silks to harvest?
A. About 5 days are required for complete pollination after the first silks appear. Harvest begins about 20 days after first silking.
Q. The germination of my Illini Xtra Sweet is low. How can I get a better stand?
A. The seeds of supersweet varieties are shrunken and do not germinate readily in cold, wet soil. Do not plant too early in the spring. Wait until the soil is warm, preferably 65°F. Sow the seed more thickly and thin if necessary. Fungicide seed treatments may also be helpful.
Q. Why don't my sweet corn ears fill out to the tips?
A. Several conditions can cause poor kernel development at the tip of the ear such as dry weather during silking and pollination; planting too close; poor fertility, lack of potassium; and poor natural pollination. These conditions may be overcome by watering in dry weather; planting at recommended spacing (9 to 12 inches in the row); proper fertilization; and planting short rows in blocks of two or more for more complete pollination.
Q. What is the best way to grow early corn?
A. Choose an early maturing variety, plant early and shallowly (about 1/2 inch deep), and cover the row with clear polyethylene film. Use 1 or 2 mil film 3 feet wide and cover the edges and ends to warm the soil around the seeds. The small plants can be left under the plastic for 2 to 4 weeks. Remove the film, or cut slits and carefully pull the plants through before the weather becomes too hot. It is wise to experiment with this technique on a small scale first. Unseasonable heat can quickly cook and kill young seedlings under clear plastic.
Q. How can I keep raccoons out of my sweet corn?
A. It is virtually impossible to keep raccoons out of garden, although many methods are employed. The most successful seems to be an electric fence made with two wires, one about 4 inches above ground level and the other at 12 inches. The fence must be operating well in advance of the time that the corn approaches maturity. Raccoons prefer to eat sweet corn in the early milk stage, just before it is ready to harvest.

Selection & Storage

Corn is a European word meaning kernel. The corn plant is native American in origin and Illinois is corn country. Driving through the state, you will see endless fields of sweet corn, feed corn, and popcorn. Small plot gardeners know that corn takes up a lot of space, it is greedy for soil nutrients, prone to weeds and disease, destroyed by small animals, wind and frost. So why do we go through all the trouble of growing corn? Because no corn is as fresh and sweet as the corn you grow yourself.
The period of peak freshness for sweet corn is measured in minutes not hours or days. The best corn is simply the freshest corn. Proper timing for harvest is crucial to the quality of sweet corn. Harvest sweet corn when the ears are full and blunt at the tip. The husks should be tightly folded and green. Using your thumb nail, poke an end kernel. It should squirt forth milky white sap. Underripe corn will contain a watery liquid; overripe corn will have a tough skinned kernel with doughy interiors. Also look at the silk, it should be turning brown and dry on the end.
Storing sweet corn for long periods of time will destroy it. The sugar quickly turns to starch, losing flavor, quality and most of all sweetness. If you must store sweet corn, use perforated plastic bags and get it into the refrigerator as soon as possible. Warm temperatures hasten the conversion process. Try to use the corn within 1 to 2 days and do not husk until just prior to cooking.

Nutritional Value & Health Benefits

Sweet corn is high in fiber, niacin, folate and some vitamin A. Folate has been found to prevent neural-tube birth defects and current research suggests that it helps to reduce the risk of heart disease and stroke. Fiber, of course, helps to keep the intestinal track running smoothly.
Nutrition Facts (Serving size: 1 ear yellow sweet corn )
Calories 83.16
Protein 2.56 grams
Carbohydrates 19.3 grams
Dietary Fiber 2.15 grams
Potassium 191.73 mg
Vitamin A 167 IU
Niacin 1.24 mg
Folate 35.73 mcg