Family: Gramineae
Genus and Species: Zea mays
Climate
Sweet corn is a warm season crop that requires a minimum soil temperature of 50°F for soil germination. For maximum growth and yield plant sweet corn in full sun.
Soil
Sweet corn thrives best in a sandy loam soil with a pH of 6.0 to 6.8. As a general guide, plant early corn in light soil (sand or loam) and late corn in heavier soil (silt, clay) when there is an option. Light soils warm up faster than heavy soils, so seed germinates more readily. Under hot, dry midsummer conditions, heavier soils have the advantage of holding much more moisture than light soil.
Sweet corn requires rich soil with ample nitrogen and moisture. Amend the soil well-aged manure or compost. Plant corn in an area that had healthy beans or peas the previous year is helpful because these legumes contribute more nitrogen to the soil especially if an inoculant was used.
Corn should be planted where the soil has been prepared to about 6"-8" deep. Make sure clumps are broken up and debris such as rocks and twigs removed.
Spacing
Corn is a tall plant susceptible to wind and therefore benefits from blocks of at least 4 rows of corn plants for support and pollination. Corn should be spaced at 8"-10" for early cultivars and 9"-12" for late cultivars, within rows spaced 30"-36" apart.
If planting more than one cultivar, space the corn stands at least 250' apart to prevent cross-pollination. An alternate method to prevent cross-pollination of different corn cultivars is to stagger planting dates of the different cultivars by a minimum of 14 days.
Direct Seeding
Sow corn seed 1" deep, 2-3 seeds per 6"-8" within rows spaced 30"-36" apart. Thin corn seedlings to 1 seedling per 6"-8". Gently tamp and rake soil smooth after planting seed.
An alternate method for planting corn is to use hills. Sow 5-6 seeds per hill. Space hills at 36" apart. Thin to 3 healthy corn seedlings per hill.
Sow corn seed no earlier than 10-14 days after the last spring frost date.
For a steady supply of sweet corn throughout the season, include early, mid-season, and late cultivars in your initial planting. 2-3 successive plantings of each corn cultivar, every 2 weeks, will extend the harvest season.
Seeding For Transplants
Corn is not normally transplanted.
Germination
These seeds germinate best in soils around 80°F-95°F.
Germination will take 7-10 days.
Watering
It is important to maintain an adequate level of soil moisture during critical periods of corn development. Corn water consumption will rise dramatically as it approaches tassel formation and silking.
A properly spaced stand of corn uses water most efficiently. Corn that is poorly spaced will experience excessive water loss from bare soil.
Harvesting
Corn is fully mature when the stalks are anywhere from 5'-7' tall or more and have at least one or two ears. Corn silk should actually start to turn brown and the kernels should be full to the touch and produce a milky white fluid when broken.
To harvest, pull down quickly on the ear of corn and turn it at the same time.
Post-Harvest Handling
Corn will quickly begin to convert sugars into starch after harvest so it is very important to quickly cool the ears after harvest. The rate of conversion of sugars to starch in the corn kernels increases with the rise of temperature.
Storage
Corn should be stored at 32°F and relative humidity of 98%-100%. In ideal conditions corn may last up to 4-6 days.
Diseases
Smut and Stewart's Disease (bacterial wilt)
Pests
Corn Borer, Corn Earworm, Flea Beetle, and Cutworm
Comments
"Normal" sweet corn (su) is corn with kernels that contain moderate but varying levels of sugar, depending on variety. Sugars convert to starches rapidly after harvest. All of the open-pollinated heirloom varieties are normal sweet corn.
"Sugar-enhanced" (se, se+, or EH) is corn with a gene that increases tenderness and sweetness. Additionally, conversion of sugar to starch is slowed.
"Super-sweet" or "Xtra-sweet" (sh2) is corn that greatly increases sweetness and slows the conversion of sugars to starch. The dry kernels (seeds) of this type are smaller and shriveled.
References
Cox, R.," Growing Sweet Corn in the Backyard Garden", Last modified 2002-04-11, Colorado State University Denver County Cooperative Extension, http://www.colostate.edu/Depts/CoopExt/4DMG/VegFruit/corn.htm, Accessed 2003-01-07.
Bradley, F. M. and Ellis, B. W.(Ed.). (1992), Rodale's All-New Encyclopedia of Organic Gardening: The Indispensable Resource for Every Gardener, Emmaus, Pennsylvania: Rodale Press.
Wells, O., "Growing Sweet Corn, Family Home & Garden Education Center", Last modified 2001-03, University of New Hampshire Cooperative Extension, http://ceinfo.unh.edu/Agriculture/growswco.pdf, Accessed 2003-01-07.