SWEET CORN
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