Corn (How to Plant, Grow & Harvest) – GIY Plants

Corn (Zea mayssubs. mays) or maize was cultivated in Mexico thousands of years ago, and there are thousands of varieties available today, making it the top commercial grain crop grown globally.

Corn is a member of the grass family (Poaceae), which includes species such as cereal (e.g. wheat, rye, oats, barley), bamboo, and common lawn grass.

Corn is used in everything from baby powder and common food products to ethanol. The delicious cobs of sweet corn, which contain up to 1,600 neatly lined, starchy sweet kernels, are a staple of county fairs and barbecues.

Unfortunately (or fortunately, depending on your stance), corn is the most genetically modified crop, with 79-95% of all U.S. corn genetically modified.

Fortunately, growing corn yourself gives you the option to select GMO or non-GMO varieties and experiment with a wide range of flavors and types.

Corn Crop Care

Corn plants range in height from 2-20 feet (60 cm to 6 m), with dwarf varieties only reaching 4-5 feet (1.2-1.5 m) – ideal for container growing.

Corn is a hungry plant, requiring lots of food, light, and water for optimal ear production. Its shallow roots make soil management also very important.

However, with full sun, plenty of garden space, and the right conditions, corn is extremely easy and relatively straightforward to grow.

Soil

Corn is a nutrient-demanding crop. Plant in a rich, loamy, slightly acidic (ph 6.0-6.5), well-draining, and fertile soil.

Amend the soil with lots of organic matter such as grass clippings to improve drainage and overall quality.

As corn is a heavy nitrogen feeder, you may want to also add some slow and fast-releasing nitrogen fertilizers such as alfalfa meal or blood meal.

Watering

Corn needs lots of watering from germination to harvest. Aim for at least one inch (2.5 cm) of water per week, especially during the critical periods when silks start forming.

Mulches may be used to retain moisture. If rainfall is short or if growing corn in sandy soils, aim to water twice a week.

Lighting

Full sun is recommended. Ideal spots in the garden are on south-facing or west-facing slopes for maximum sunlight.

Humidity & Temperature

Maize requires relatively high humidities between 55-65%.

Ideal growing temperatures are between 70-86°F (21-30°C) in the daytime and around 57°F (14°C) at night.

Temperatures above 92°F (33°C) may cause heat stress and temperatures below freezing (32°F or 0°C) will kill plants.

Fertilizing

Corn requires lots of nutrients, so apply a 10-10-10 NPK fertilizer (3-4 lbs per 100 square feet) before seeding.

Side-dress the plant with more fertilizer (8 oz or 30 g per 10 linear feet or 3 m) when it reaches 12 inches (0.3 m). Water after fertilizing.

Blood meal or alfalfa meal works well as fertilizer but avoid manure.

Diseases & Pests

Corn diseases, such as the ones described below frequently damage crops:

• Bacterial soft rot causes rapid drying out of younger leaves followed by leaf tissue rot. The rot causes an unpleasant odor and may kill plants. Avoid sprinkler irrigation which is a frequent cause.

• Fusarium ear rot causes white to pink discoloration on kernels. In severe cases, the fungus may entirely consume the ears, leaving husks cemented to kernels. Resistant hybrids and earlier planting help avoid Fusarium rot.

• Common smut (boil smut) causes tumor-like galls to form on above-ground parts. As galls mature, they turn into masses of powdery, dark-olive brown to black spores. To prevent smut, avoid injuring crops, practice crop rotation, and use resistant hybrids.

• Common rust causes yellow patches of pustules to develop on leaves. These golden brown pustules may erupt and become powdery before maturing into black spores.

• Corn stunt is a bacterial infection that results in stunted plants. Stalks will develop multiple small ears and cause kernels to be loose. Yellowing of leaves near the top of the plant is common. Early planting will help prevent corn stunts.

• Corn mosaic viruses (several strains) cause narrow, light green to yellow streaks on leaves. Plants may become stunted and predisposed to ear and stalk rot. Control aphids to prevent spread.

• Other diseases include anthracnose, downy mildew, bacterial stalk rot, gray leaf spot, and nematodes.

Corn is susceptible to many types of insects, with some common ones described below:

• Stem (stalk) borer and sorghum borer – Adult moths of these similar insects lay eggs on leaves, where larvae will eat leaves before feeding on stems and later cobs.

• African armyworms lay pale green to pink eggs covered with white cottony material. Armyworms themselves are thin, greenish-brown in color, and will feed on ears and tassels, which severely damage crops.

• Corn earworms – Mostly active at night, these olive green, tan, to dark reddish-brown colored worms lay tiny white eggs throughout the growing season. Larvae are greenish in color and have black heads with black hairs. These pests feed on leaves, tassels, silks, whorls, and ears of mostly sweet corn.

• Cutworms lay eggs that are mostly white to dull or off-white in color and ribbed. Adults curl into a C-shape when disturbed and typically feed on plants at the base near or below the soil surface.

• Corn leafhoppers – These light-tan pests have two dark spots between their eyes, feed on corn juices, and transmit diseases such as Mosaic Streak Virus (MSV) which stunts growth.

• Grasshoppers feed on foliage and occasionally appear in late summer and fall.

• Other common pests frequently also seen in other crops include aphids, cucumber beetles, spider mites, and thrips. [1]

To control most pests, plant early, select disease and pest-resistant cultivars, practice crop rotation, grow with pest-warding companion crops, and (if necessary) use insecticides.

Harvesting/Days to maturity

Corn can take anywhere from 50-365 days to mature, depending on the cultivar, but averages between 90-120 days to reach harvesting maturity for most types.

Examples of early maturing varieties include Earlivee (58 days), Seneca Horizon (65 days), Catalyst XR (66 days), and Spring Treat (66-67 days), among others.

Corn Origin (man-made)

Corn (Zea mayssubs. mays) or maize does not grow naturally in the wild and requires human cultivation.

Humans have been selectively cultivating corn for thousands of years, resulting in the thousands of different varieties of corn we know today.

It is widely believed that corn originated in southwestern Mexico over 8,700 years ago from teosinte, a wild species of grass.

Genetic analysis showed that it diffused south to Peru and north to the Southwestern U.S. [2]

How to plant corn

Corn can be a bit temperamental when it comes to planting depth, temperature, and water levels, with some seeds rotting in the ground and experiencing other problems before sprouting.

A good tip is to grow seeds indoors, one week before the last frost, and then transplant seedlings to the garden one week after the last frost. Seedlings should have one foot (0.3 m) of space in all directions.

If sowing seeds directly in the garden, plant them at a depth of one inch (2.5 cm), spaced 1 foot (0.3 m) apart, and after the last frost.

Make sure temperatures are above 50°F (10°C), but ideally between 70-86°F (21-30°C). Water daily until seeds sprout above the soil (~4-5 days).

Corn growing stages

Corn is typically divided into two key stages (vegetative and reproductive) summarized below:

Vegetative Stages	Reproductive Stages
VE (Emergence)	R1 (silking)
V1 (first leaf)	R2 (blister)
V2 (second leaf)	R3 (milk)
V3 (third leaf)	R4 (dough)
V(n) (nth leaf)	R5 (dent)
VT (tasseling)	R6 (physiological maturity)

Days 1-29

• VE – Germination starts when the seeds have at least 30% moisture. Exposure to water temperatures below 50°F (10°C) 24-36 hours after planting will kill seeds.

Roots and shoots will grow at this stage eventually emerging from the soil in 4-6 days, or up to two weeks in cold climates.

• V1-V6 – Leaves start forming. Fertilize to encourage root growth. Frost damage at this stage may destroy leaves, but not the parts below ground.

By V5, leaf and ear shoots are starting to form. You may also begin to see a microscopic tassel emerging. Plants should be about 8 in. (20 cm) by this stage.

• V6-8 – By V6, fertilize again to encourage leaf growth. By V8, nutrient deficiencies, if any, will become obvious. If leaves are not growing, apply some rescue fertilizer with nutrients N, K, S, and Zn. Ear shoots will also begin forming.

Days 30-60

• V10-V18 – New leaves start forming more rapidly, appearing every 2-3 days. Moisture stress will affect ear and kernel development significantly during these stages. By V18 or V16 (in early developing hybrids), plants should be ~4 feet (1.2 m) or taller.

• VT (tasseling) – All leaves should develop and tassels should be visible. Corn silks (thread-like fiber) should emerge in 2-3 days from ears. Pollen will begin to shed for the next 1-2 weeks. Pollination is critical for viable kernels at this stage. Consider shaking to loosen pollen.

Day 60-90

• R1 (silking) – One or more wet silks should extend outside of husk leaves to receive pollen.

• R2 (blister) – Silks will darken and dry out after pollination (~12 days after beginning to silk). White kernels inside the ears will form “blisters” with clear liquid.

• R3 (milk) – 20 days after silking, kernels will be yellow with a clear “milky” and starchy fluid inside.

Day 90-120

• R4 (dough) – The starchy liquid inside the kernels will have a dough-like consistency. Kernels may start developing dents on them.

• R5 (dent) – All kernels are dented. Cobs will be either white, pink, or red in color.

• R6 (maturity) – A “black layer” will form at the kernel base 2-3 days after maturity. [3]

Types of Corn

Corn varieties are typically categorized into 6-7 types based on the hardness of their endosperm (tissue surrounding the seeds): flour, flint, dent, pop, waxy, sweet, and pod corn.

Below are the types of corn and their common uses:

• Flour corn (Z. mays amylacea) is ground into fine corn flour.

• Flint corn (Z. mays indurata) is often used to make coarse cornmeal.

• Dent corn  (aka field corn; Z. mays indentata), the most commonly grown in the U.S., is used in animal feeds and industry.

• Pop corn (Z. mays everta) is, as expected, used to make popcorn.

• Waxy corn (Z. mays ceratina) is a glutinous (100% amylopectin; no amylose) type of corn that is mostly grown in East Asia as a substitute for starch.

• Sweet corn (Z. mays saccharata) is primarily eaten on the cob or canned and frozen.

• Pod corn (Z. mays tunicata) is the most primitive form of corn similar to the wild maize grown for thousands of years in the Americas. It is mostly grown ornamentally.

Sweet corn is further divided into three categories based on genetics and sugar levels (lowest to highest): normal sugary (Su), Sugary Enhances (Se), and Supersweet (Sh2).

When planting sweet corn, separate them from field corn to avoid accidental cross-pollination, which results in unsweetened kernels.

Corn Benefits

Corn is rich in fiber, vitamins, and minerals. 100 g of corn contains:

• 76 g of water
• 86 calories
• 3.22 g of protein
• 1.18 g of fat
• 19 g of carbs
• 2.7 g of fiber
• 3.22 g of sugar
• Varying amounts of calcium, iron, magnesium, phosphorus, potassium, sodium, zinc, copper, manganese, selenium, and vitamins A-C.

Below, we summarize all of the beneficial ingredients often found in corn and their purported benefits:

Key Nutrients	Purported Benefits
water	Hydration and body temperature regulation
starch and fiber	Aids in digestion and beneficial for teeth and gums; starch and sugars, however, may raise blood sugar
lutein and zeaxanthin (carotenoids)	May benefit eye health
potassium, magnesium, iron, phosphorous, zinc, copper, selenium	Helpful for regulating blood pressure and hydration levels; promotes heart health, among other mineral benefits
Quercetin	An antioxidant that’s believed to help with inflammation of the prostate; found often in blue or purple corn
vitamin C	Protects the body from cellular damage; strengthens the immune system and may help lower blood pressure; involved in collagen production and iron absorption
vitamin B (thiamine, folate)	Helps convert carbohydrates into energy; folate is important during pregnancy for fetal health
vitamin A	Great for skin; Benefits vision and immune systems

It’s better to eat corn raw, as processed corn (e.g. syrup, chips, and oils) loses beneficial fiber and nutrients during production, and has high amounts of salt, sugar, and fat added.

Growing Corn in containers

It’s possible to grow corn from containers, but yields may be less than corn grown in gardens.

To plant in a container, use a large well-draining pot at least 12 inches (30 cm) deep and wide. Consider a barrel pot to ensure enough room to grow the “Three Sisters” crops: corn, squash, and beans.

Sow 4-6 seeds per pot about 1 inch (2.5 cm) deep in a well-fertilized, loamy soil. It’s better to have at least a few stalks growing together as that will ensure pollination.

Dwarf varieties such as “Trinity” and “Sweet Painted Mountain” are ideal for container pots as they do not exceed 4-5 feet (1.2-1.5 m) in height.

Varieties such as “Burpee’s On Deck” and “Gurney’s Utopia” have been specialized for container growing.

Corn companion plants

Corn, bean, and squash are referred to as “the Three Sisters Garden” for their compatibility together.

However, there are several other crops you can grow with corn as well:

• Other legumes (e.g. peas, peanuts, clovers, and lentils) are all great nitrogen-fixers, increasing organic soil matter, which corn loves. The corn also acts as trellises for these plants.

• Cucurbits (e.g. squash, pumpkins, zucchini, cucumbers, melons, etc.) spread along the ground, suppressing weeds and keeping soils moist and nutritious. They also benefit from the shading corn provides.

• Some herbs such as basil, catnip, thyme, chives, dill, mint, nasturtiums, and oregano help repel pests.

• Sunflowers help act as windbreakers for corn and invite ladybugs, which control aphids and other pests.

• Spinach also grows well in corn’s shade and helps keep corn roots cool.

• Radishes will keep cucumber beetles, squash borers, and corn borers away.

Avoid brassicas (cabbage, broccoli, or kale), as they require lots of sunshine, which corn may block out.

Tomatoes are heavy feeders, competing with corn and inviting pests such as corn earworms, so they should be avoided as well.

Eggplants also invite pests that also affect corn.

Corn vs Maize

Corn and maize refer to the same crop. Corn originates from British English, where the word corn generally refers to the main crop grown in a locality. In England, wheat was called corn, and in Scotland and Ireland, oats were called corn.

The crop grown by Native Americans was, thus, referred to by Americans and the British as : Indian corn, but the word Indian has since been dropped.

Maize, on the other hand, comes to us directly from the Taíno, the Native Americans who introduced the crop to Columbus. The Taíno referred to corn as mahiz, which the Spanish adopted as maíz before being Anglicized to maize.

Today, only Americans, Canadians, and Australians refer to the crop as corn, while the British and scientific community have adopted maize for its lack of confusion.

Frequently Asked Questions

References:

[1] Unknown Authors (various dates). How to Manage Pests – Corn. University of California Agriculture & Natural Resources. http://ipm.ucanr.edu/PMG/selectnewpest.corn.html.

[2] Jones, M. O. (2017, December 15). Corn: A Global History (Edible). Reaktion Books.

[3] Berglund, D. (2022, May). Corn Growth and Management Quick Guide. North Dakota State University Agriculture and Extension. https://www.ndsu.edu/agriculture/ag-hub/publications/ corn-growth-and-management-quick-guide.