Sweet Corn Growing and Harvesting Information
| Temperature | |
| Germination | 60-95F |
| For Growth | 60-75 F |
| Soil and Water | |
| Fertilizer - Heavy feeder; apply manure in the fall, or compost a few weeks before planting. | |
| Side-dressing - Apply every 2 weeks and additionally when stalks are 8-10" and knee high | |
| pH | 5.5-7.0 |
| Water | average |
| Measurements | |
| Planting depth | 1/2- 2" |
| Root depth | 18"-6' |
| Height | 7-8' |
| Width | 18-48" |
| Space between plants | |
| In beds | 8-12" |
| In rows | 18" |
| Space between rows | 30-42" |
| Average plants per person | 12-40 |
| Harvest | |
| Sweet corn: About 18 days after silks appear, when they're dark and dry, make a small slit in the husk (don't pull the silks down), and pierce the kernel with a fingernail. If the liquid is (1) clear, wait a few days to pick, (2) milky, pick and eat, or (3) pasty, the ear is past its prime and best for canning. Popcorn: Pick when the husks are brown and partly dried. Finish drying corn on the husks. A solar drier is the most rapid method, drying the corn in about 5 days. The kernels are ready for storage if they fall off easily when rubbed by a thumb or twisted. Before using, store in bags or jars to even out moisture content. The ultimate test, of course, is to pop them. After harvest: Cut stalks and till under or compost immediately. | |
| First Seed starting Date: 4-11 days before last frost date | |
| Last Seed Starting Date: 97-127 Days before first frost date | |
| Companions | |
| Companions: cucumber, melon, pumpkin, squash | |
| Incompatibles: tomato (attacked by similar insects) | |
Corn is one of the most popular crops for the vegetable garden.
Generally speaking, corn takes a large amount of room, water,
sunlight, and nutrients compared to other home garden crops, but the
rewards can be sweet. There is only one way to truly enjoy the
flavor of fresh corn: Grow it yourself - for corn loses much
of its sweetness within minutes after picking. True corn
lovers start water boiling on the stove before the pick, so that
they can rich the tender ears strait from the garden into the pot.
Corn is a warm-season crop, tender to frost and light freezes.
Many types are grown, including field corn, ornamental corn,
popcorn, sweet corn, and even broomcorn. Corn may be white,
yellow, bicolor and many shades of red, blue, or even black.
Typical sweet corn, probably the most popular for home gardens is
usually either white or yellow, we will focus on these. The earliest
corn matures in about two months, the latest in 3. Many
gardeners plant early, mid, and late season varieties at the same
time to extend the harvesting season. Another option to extend
harvesting would be to make succession plantings of an early, fast
maturing variety every 10 days or so until midsummer. A
second planting should not be made until the first planting has 3-5
leaves. It should be noted that the later sweet corn matures, the
more difficult insect control will be.
Where to Grow Corn
Corn requires three months of warm, sunny weather to mature, and can grow wherever ample water is available. In cold northern climates with shorter growing seasons (65 days) such as Alaska and northern Canada dwarf varieties can be grown.
Reccomended Varieties of Corn
There are three major types of sweet or supersweet corn marked to
home gardeners. The traditional type is referred to as
"sugary" and is typically denoted by the letters "su." The
second type of supersweet corn has a very high sugar content and
extremely shrunken seeds due to a small, weak embryo. This
type is often marketed as "extra sweet" or "ultrasweet" and is
usually referred to by the letters "sh2" for shrunken.
The third type is also a supersweet corn. It tends to have a
higher sugar content and to maintain or extend this sugar content
longer on the plant and after harvest. It us usually referred
to as "se" for "sugar extended." Se corn tends to be very
sweet, tender, and crisp and usually retains these qualities after
harvest. However, its requirements for warm soil temperatures
at germination and isolation from some other corn types at
pollination make it more difficult to grow.
There are also the ornamental varieties, with colored kernels.
These varieties should be grown away from sweet corn, to avoid any
cross pollination.
The trick to enjoying an extended corn harvest is planting a span of varieties (early, midseason,
and late) to spread the harvest over a long season.
There are several hundred good varieties of sweet and super sweet
corn available. Recommended early varieties include:
Early - Spring Gold, Seneca Explorer
Midseason - Sundance; Wonderful; Northern Bell; Gold Cup;
Golden Cross Bantam.
Late - Seneca Chief; Silver Queen and Country Gentleman Hybrid
(white);Sweet Sue; Butter and Sugar; Sugar and Gold (all bicolor)
Dwarf - White Midget; Golden Midget; Midget Hybrid
Popcorn - White Cloud; Japanese Hillless
VARITIES
'Early
Sunglow' and 'Early Xtra-Sweet' which are yellow, and 'Silver
Sweet', a white corn. Good midseason corn includes 'Honey and
Cream' (also called 'Butter and Sugar'), a yellow and white type;
yellow 'Barbeque'; and white 'Snowcrest.' Popular late
varieties are yellow 'Golden Cross Bantam' and white 'Silver Queen
Hybrid.'
Soil for Corn
Average garden soil will support a good corn crop, but the best results are obtained when the ground is deeply prepared with well-rotted manure and compost to provide a light, well-draining texture. Corn is a heavy feeder, and needs generous quantities of nutrients, especially phosphorus and potash. Work in one pound of 5-10-10 or 4-8-12 per 25 feet of row, or work bone meal and wood ash into the top 8-10 inches of soil before planting. Remove any weeds, rocks, and trash as you work the soil As always, only work the soil when it is dry enough not to stick to the garden tools. If hills are planted, place a scant handful of fertilizer in the bottom of the hill and work it in well before planting the seed. Or follow the Indian advice to the Colonists and work in fish heads and entrails deeply before sowing seeds.
Planting Corn
Germination in 7-10 days.
When - Sweet corn is a warm-season crop that germinates and
grows poorly during cool weather, and should only be planted when
there is no more danger of frost. The soil must be warm (55-60 degrees) and days and
nights warm before corn can be planted, as it is susceptible to
frost and cool weather. The easiest way to prolong harvest is
to plant early, midseason, and late varieties at the same time.
Or if you family has one favorite variety, then plantings can be
made every two weeks until 3 months before the first frost. The supersweet and extra sweet varieties are even more sensitive to cool
weather and are not normally planted until the soil temperature
reaches 60 F. Corn should generally be planted on the northern
side of the garden because they get tall and can easily shade the
other garden crops, reducing their yield.
How - Corn should be planted in a square block area with at
least 4-6 adjacent rows of the same variety, never in one long row, as
it is open-wind pollinated and needs neighboring corn plants for
good formulation of well-filled (pollinated) ears of corn.
Gaps in ripe ears are caused by poor pollination. The best
planting depth varies with soil types and with the time of planting.
Plant deeper in light soils and shallower in heavy soils.
Early plantings should be shallower than later plantings because
better moisture and warmer temperatures exist near the surface.
If late plantings are shallow (1/2 inch) there is less likelihood
that seed will germinate. A good rule of thumb is to plant
seeds 3 times deeper than their average diameter. Place rows 3
feet apart. Plant 4-5 seeds per foot, 1/2 - 2 inches deep,
thinning to 10-12 inches between plants. (Plant dwarf variety
seeds 1 inch deep, 30 inches between rows, 8 inches between plants.)
Or place corn in hills 3 feet apart, with 4-5 seeds per hill,
thinned to the 3 strongest plants. The seeding rate should be
about 1 to 2 ounces of large-seeded varieties or about 1 oz of sh2
types per 100 feet of row. Seeding at this rate will provide a
good plant population if growing conditions are favorable.
Plant Spacing for small gardens
In areas with unlimited space, sweet corn is usually spaced 10-15
inches apart within the rows, with each row about 36-42 inches
apart. A common mistake made by home gardeners is to plant
sweet corn in only one or two rows at a time. This typically
results in poor pollination and low yields. Sweet corn grows
best when planted in several short rows instead of one long row.
Corn has male flowers on top of the plant and female flowers called
silks at leaf axis along the main stem. The tassel can produce
up to a million pollen grains. Pollen moves by wind and
gravity, so single rows of corn don't pollinate and produce as many
ears of corn as do rows side by side.
Plant small quantities of sweet corn in rectangular blocks that
consist of a minimum of three rows. Plant the seed about 3-4
inches apart in the row, and space the rows 2 1/2 to 3 feet apart.
After the plants are up, thin them to 12 inches apart. If
planted closer together, the corn will have small, poorly filled
ears. In small areas having limited space, but with good soil
moisture and organic matter, it is possible to plant double rows
that are 10-12 inches apart with 30-42 inches between each double
row. Plants within each row are spaced about 12 inches apart.
Planting at these spacing will provide good pollination and good
yields as long as the blocks are no more than three or four sets of
double rows wide and proper moisture, nitrogen and weed control are
provided. This method offers the most efficient use of the
garden area. Otherwise plan on spacing the plants 1 foot apart
within the row, and the rows about 2-3 feet apart.
Isolation
Most gardeners know that sweet corn may not be as sweet if it
crosses with field corn. Likewise, some of the supersweet or
extrasweet corns may not be as sweet if they cross with other types
of corn or even with other supersweet varieties. Corn verities
can be prevented from crossing by isolating them from each other.
They can be isolated by either planting them 100 yards or more
apart, or by timing plantings so each variety sheds pollen at a different
time. It is also a good idea to isolate different sweet corn
types from each other, unless the effects of crossing them is established.
How Corn Grows
Corn is a monocotyledon, a grass-like plant, as are wheat, oats, lilies, and orchids. It will grow to 4-5 feet tall on a thick hollow stalk that supports long (2-3 foot) leathery leaves. As the plant matures, the tassel or pollen lowers will appear at the top, and from the leaf axis the small, sheathed ears will appear, with soft silk threads hanging from them. These are the female seed-bearing parts of the corn plant, the ones that receive the pollen. The ears will swell and develop into corn kernels along a central cob as pollination takes place. Sucker may also develop from corn plants, and sometimes they may even produce an ear. Usually two ears grow on each corn plant. Once pollinated, corn matures rapidly, usually 15-20 days after the first silks appear.
Cultivating Corn
Corn must be kept weed free, and shallow cultivation is important
until the tassels appear. Then stop cultivating. The
extra "prop" roots will start to develop above ground as the corn
matures, and these can be hilled up to give the plants extra strong
footing.. Watering will be important if the
growing season is dry, especially after tassels form. Water
deeply weekly if there is no rainfall. Corn has shallow roots, so mulch heavily and avoid cultivating
deeper than 1 1/2 inches. In small patches, don't remove suckers,
they may bear corn if well side-dressed.
Fertilization
Sweet corn is a heavy user of nitrogen, so good yields depend upon
adequate levels being present. Once it sprouts, it grows
rapidly and consumes large amounts of soil nutrients; so it is
important to fertilize. When stalks are 6-10 inches tall spread a
band of 5-10-5 fertilizer on both sides of each row - about 1/2
pound per 25 feet of row. If you have covered the ground with
mulch, pull it aside before applying the fertilizer, or use a water
soluble fertilizer that you can pour over the mulch, and respray at 5 day intervals at least 3 times. When sweet corn is about 2 feet tall, apply 1 cup fertilizer
for every 10 feet of row. Scatter evenly between the rows, mix
lightly with the soil, and water when finished. Proper
nitrogen fertilization is very important to develop a strong tall
stalk with the se or sh2 types. Side dress corn twice as it is
growing, once when plants are about 6 inches high, and again when
they are about knee high. Spread a band of fertilizer along
the row and work in lightly, using either 5-10-10 of 4-8-12 or a
favorite organic high in phosphorous and potash. If corn
leaves are yellowing or "firing" they need nitrogen
Weed Control
If fertilized as recommended, weeds will flourish in the rich soil
and rob nutrients from the corn. Weeding is vital, but be sure
not to damage the corn's shallow roots. Control weeds by
preventing them from becoming established. This means that
weeds should be removed while both the corn and the weeds are small.
If double rows are grown, a rototiller can be used between each set
of double rows, and hand tools can be used between the double rows.
If weeds are removed while they are small, corn will grow at a rapid
rate and will reduce weed seed emergence as the corn gradually
shades the soil.
Irrigation
Sweet corn is a high user of water and requires adequate moisture
throughout the growing season to keep from wilting, especially if
the double-row technique used. Water may be applied by a
trickle or sprinkler irrigation. It should be provided
throughout the season, but is more important during germination,
tassel and silk formation.
Water for irrigation can be applied with a sprinkler. A common
mistake of home gardeners is to assume that wetting the surface is
all that is needed when using the sprinkler. It is important
to wet the effective root zone of the plant. This means that
the depth of the soil containing larger percentage of active
roots should be moistened as well. Usually this is the top
8-12 inches. An easy way to do this is physically check the
depth of wetting after the system has run for a period of time.
When the soil is moist to the required depth, shut the system off.
A trickle system can also be connected directly to the household
watering system through a hose and filter connections. It only
requires 8-10 pounds of inline pressure to operate a trickle system.
Plastic hose with properly spaced emitters can be laid down each row
to deliver water the base of each plant. This places water
where it is needed most and is utilized the most efficiently.
Trickle water systems are more efficient and consume considerably
less water than sprinkler systems with the same end results, but are
more laborious and costly to install and manage.
| Storage Requirements | ||
| Corn is best eaten immediately. Some gardeners won't even go pick their ears until the cooking water is already boiling. | ||
| Fresh | ||
| Temperature | Humidity | Storage Life |
| 40-45F | 80-95% | 4-10 days |
| Preserved | ||
| Method | Taste | Shelf Life |
| Canned | excellent | 12+ months |
| Frozen | good | 8 months |
| Dried | good | 12+ months |
Harvesting Corn
2 1/2 to 3 months. There is an old New England saying
that "corn is picked when the cooking water starts to boil."
Corn sugar will start to turn to starch as soon as the ear is taken
from the plant. To capture the sweetest flavor, pick just
before preparing the dinner, or leave unhusked and refrigerate until
cooking time.
In general, harvest corn while it is young, or it will lose it
sweetness, as the sugar turns to starch. The best time to pick
corn is early in the morning or evening when it is cool. Test
each ear for ripeness. Juice from the kernels should be milky
white and the kernels should be soft. The silk on the ears
should have turned dark brown. The ears should be firm.
Kernels on the tips of the unhusked ears should be plump and milky.
Sweet corn is not ready when the juice of the kernel is watery.
It is overripe when the kernels get large, chewy and pasty like
dough. To harvest ears, hold the stalk below the
ear. Twist the tip of the ear toward the ground until it
breaks off.
To protect your next year's crop, destroy old corn stalks and
stubble, which can harbor corn borer larvae over the winter.
HANDLING AND STORAGE
Handling and Storage
If sweet corn is to be frozen or canned, it should be shucked, de-silked,
and brought to a boil for a period of three minutes immediately
after harvest. Cool it as rapidly as possible after boiling.
It may them be either frozen or canned. Immediate processing
in this manner reduces sugar loss and greatly improves flavor.
Avoid holding sweet corn for long periods of time at ambient
temperatures after it is harvested.
Corn Pests
-Corn ear worm - A very destructive pest of corn that works its
way down into the ears and destroys the kernels. Control with
mineral oil squirted down into the silks 3-7 days after they appear.
Some of the newer varieties offer some resistance to ear worms: Honeycross, Seneca Chief, Spring Gold, Butter and Sugar.
- European corn borer - Corn borers feed on the
foliage and internal portions of the stalk. They are usually
identified by insect holes bored into the stalk and droppings on the
foliage. They will bore overwinter in corn stalks, so fall cleanup is essential.
Delay planting of corn to miss the first brood, then plant the
midseason varieties. European corn borer control is difficult
for home gardeners because sprays are effective only during the two
to three day period after eggs hatch and before larvae bore into the
stalks. Pay close attention to the presence of eggs.
Eggs are white and one-half the size of a pinhead. They are
laid in masses that overlap like fish scales. Eggs darken just
before hatching. To control, use the recommended insecticides.
Two or more treatments may be needed weekly, since four generations
may occur each season.
- Japanese beetles - Japanese beetles normally congregate on the
tip of the ear and feed on the silks. This may reduce
pollination and yields. Can usually be effectively controlled
by applying recommended insecticides as a foliar spray directly to
the silk when it first appears, and continuing weekly until harvest.
If birds are a problem in your garden, stealing seeds or eating
seedlings, cover your corn patch with a floating row cover
immediately after planting seeds.
Corn Diseases
Corn smut - A disfiguring parasitical fungus that forms large "boils" on stalks, leaves, tassels, or ears, prevalent in hot, dry weather. The case splits apart and spreads inky black dusty spores. At first appearance, the spore cases should be cut off and burned. It is essential to cut off the cases before they burst, as the spores are viable for 5-7 years.
