Corn (Gramineae Zea)

Place of origin: Mexico, Andes region
Proper temperatures for germination 60-80°F 25~30°C
Proper temperatures for plant growth 65-80°F 18~30°C

Characteristics Scientific name: Zea Mays

There are various types of corns. Edible corns are sweet corn varieties and flint corn. Native or heirloom corn comes in many varieties that include Golden Bantam, Hop McConnell Speckled, pop corn, and meal varieties and can be white, black, yellow or red. Because of its taproot, corn isn’t suited to transplanting. Sweet corn is suited to warm weather and needs a lot of sun and rainfall.


When the average temperature is around 60°F, 15°C, (without fear of late frost), sow seeds.
Even if seeding is delayed, yield is not affected very much. For easy germination, before sowing, soaks seeds in water over night. When sowing seeds in two lines, the width of ridge should be one about one yard (1 m), but if sowing seeds in a single line, the width of ridge should be about 24-32” (60-80 cm). Sow a few seeds in each spot with the space of 12-15” (30-40 cm) between seeding spots. As seeds are large, cover seeds with ½-1” ( 2-3 cm) of soil, and lightly press down. At optimal temperatures, seeds germinate in 5-6 days.
※ If seeds are sown too closely, the number of seedlings increases, but ears don’t develop well.

Growing seedlings/Permanent planting

It is possible to harvest corn earlier by growing seedlings. As corn damages easily when transplanting, grow seedlings in pots and then plant seedlings carefully. Once planted, corn cannot be moved. Choose the proper size of pots according to the size of the seedlings.

Thinning/Gathering soil

Once three or four leaves appear after germination, thin out poor or deformed seedlings and grow remaining seedling individually. In the early stages of plant growth, practice intertillage slightly and gather the soil, which is effective for weeding and prevents the seedlings from falling down around the plant. (It is good to practice intertillage and gathering soil a month after germination.) Intertillage in the middle and late stages of plant growth causes root damage and can cause the plant to fall over. Besides, when the soil is dry, intertillage dries the soil out more and promotes drought damage. Therefore, decide whether intertillage is appropriate or not, according to the situation.

Axillary buds

Axillary buds have an important role in providing the energy generated by photosynthesis to the underground part of plant. Therefore, remove axillary buds according to the variety or the soil’s condition.

It is especially important not to remove the axillary buds of early harvest varieties because their leaf area is small. For middle and late harvest varieties, remove the first axillary bud once and then leave the weaker axillary buds that come out later. If all axillary buds are left on seedlings, the ears grow small. If axillary buds are removed after they are large, the main stem is sometimes affected badly, so remove the axillary buds when they are as small as possible. With frequent watering, it is possible to grow plants without removing axillary buds. As the amount of water evaporating from leaves is large, adjust the amount of water given. In arid areas, in order to reduce the amount of water evaporating from leaves, remove all axillary buds.


Just before ears develop a great amount of watering is needed. If water is scarce in this period, ears don’t enlarge well and tip infertility easily occurs, so diligent watering is needed. In this period (about a month around the time that ears emerge), if fine days continue, water frequently.


As corn is a cross-pollinating crop, don’t plant seedlings in a single line. Plant the seedlings in several lines, which helps pollination occur easily. As aphids are attracted to male corn flowers, the male flowers can be removed after pollination as a way of reducing insect damage.


The proper time to harvest sweet corn is when the corn silk becomes brown and withers completely. As the harvesting period is short, seeds can be sown several times to stagger the harvest. As sweet corn plants grow large and the fruit ripens, the sugar content decreases and the starch content increases. (As sweet corn plants have the highest sugar content in the morning, harvest early in the morning. The plants have the lowest sugar content in the evening.) After harvesting, as time goes by, the sugar content decreases and corn loses its sweet flavor. Therefore, it is good to eat the corn just after harvesting or to keep the corn in the refrigerator.

For hard varieties, harvest ripe corn when the ears are completely dry.

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