Corn, most countries know it as maize – and it’s been cultivated for thousands of years! It’s used in a variety of food items from oils to cereals, but corn on its own is often a staple dinner item.
In this video and below transcript, we'll be walking you through:
Glossary of corn terms
Varieties of corn
Starting your corn seeds
Caring for your corn
Fertilizer and/or Mulching
Transplanting best practices
Companion Plants do’s and don’ts
Growing structure options
Common Problems and Their Solutions
Pests, Diseases, Deficiencies
Harvesting and Storing
GLOSSARY OF CORN TERMS
HYBRIDIZATION: The process of crossing the pollen of one variety with the receptive female flowers of another variety. This technique allows more uniform maturity, plus improved quality and disease resistance. It’s important to note that hybrids are isolated gene groups, not genetically modified (GMO).
EARS: The corn cob itself – which is closely wrapped in the green husks.
HEAT UNITS: The accumulated heat the plant has had while growing, which controls the maturity of the ears. The plant itself can grow in almost every soil, but this doesn’t mean that the ears will mature.
TASSEL: This is the male part of the plant which sits on top of the mature corn crop.
SILK: The female part of the corn plant that grows on top of the ears.
WIND POLLINATED: When a plant pollinates itself or gets pollinated by a similar variety. The wind moves the pollen from the tassel at the top of the plant to the silks of the ears.
It’s difficult to maintain the vigor and sweetness in open pollinated varieties, so hybrids are typically used instead.
VARIETIES OF CORN
The differences between the varieties lie in the kernel color (white, yellow, bicolor), ear size, and sweetness.
This type is flavorful, stress-tolerant, and vigorous.
It’s not as sweet as other hybrid varieties, because its sugar turns into starch quickly after picking.
The kernels are tender and creamy - but when the sugar turns into starch, they get chewy.
SUGAR-ENHANCED (SE, SE+, EH, EVERLASTING HERITAGE):
This type falls between normal and super sweet in terms of stress tolerance, vigor, sweetness, flavor, and how fast its sugar turns into starch.
SUPERSWEET (SH2, SHRUNKEN)
This type of corn contains two to three times more sugar than other hybrids. The sugar in the kernels turns into starch very slowly, giving them a much wider harvest window.
They have a crispy texture, are less creamy, and are more easily stressed by cold and other problems.
This type also needs to be isolated from normal and sugar-enhanced varieties in order to pollinate.
PLANTING YOUR CORN
Corn germinates best in soil that is between 65° and 95°F (18° and 35°C), and if the soil isn’t warm enough, the seeds will rot before they can germinate. It’s best to always start outside after the last frost.
Most gardeners plant fungicide treated seeds, but if you want to use untreated seeds instead, make sure that your soil has properly warmed up to at least 65°F.
If your soil is cooler than that, it’s more likely your seeds will get infected by diseases.
When you start different varieties with varying maturities, you can have a longer harvest season. But make sure not to plant the sh2 variety next to su and se/se+ varieties.
If possible, plant your seeds in blocks of at least 4 rows for good wind pollination.
Plant your seeds 1- 2 inches (2-5cm) deep unless you have sh2 seed, which you’ll want to either plant shallower or in cool soil.
Keep your seeds about 4-6 inches (10 to 15cm) apart, in rows that are 30 to 36 inches (76-91cm) apart.
SUPPORTING YOUR CORN AS IT GROWS
Corn grows well in USDA zones 4 through 8 – but its success is more about the summer heat it gets (aka heat units).
Their ideal soil pH is 5.8 – 6.8, and the soil needs to be nice and fertile.
Keep in mind that corn is a heavy feeder, so nitrogen is an especially important nutrient supply.
Keep in mind that it’s not necessary to remove side-sprouts from your corn plant. In reality, removing them may actually reduce your yields!
CARING FOR YOUR CORN CROP
STEP 1: Mount some soil around the stems of your plant when it’s about 6 inches (15cm) tall. This anchors your corn, keeping its roots covered and cool.
STEP 2: When plants are 3 to 4 inches tall, you can thin them to 8-12 inches (20-30cm) for ideal spacing.
STEP 3: Control any weed growth until your crop is about knee high, then leave it alone. Corn will actually form a canopy of leaves that will keep new weeds from growing.
STEP 4: Give your corn about 1 inch of water per week – and make sure not to let your plants suffer from a lack of water while the kernels are forming. It’s during this part of the growing process that it needs water the most.
STEP 5: Corn has a shallow root system, so don’t cultivate too deeply, or you could damage your plants. You will see many new roots developing above the soil. These are not for water or nutrient absorption, but simply to stabilize the plant as it grows taller!
FERTILIZER AND/OR MULCHING
Since corn is a heavy feeder, you’ll need to use manure or compost as well as fertilizer.
You can use 1 lb (500g) of a complete organic fertilizer per 60 feet (6m) of row, by mixing it thoroughly into each seed furrow (a long narrow trench).
When your corn plants are about 2 feet tall or have 8-10 leaves, reapply 1 cup of fertilizer for every 10 feet of garden row. Scatter it evenly between the rows, mix it with the soil, then water your plants.
As well, mulching helps to maintain soil moisture and control weed growth. Wood chips, uninfected plant residue, or straw are all great options to use.
TRANSPLANTING BEST PRACTICES
Although we don’t recommend it, you can start corn seeds inside and transplant them outdoors once the temperatures are warm enough.
You can start about 3-4 weeks before you plan to transplant your seedlings outside.
Just keep in mind that corn plants grow best when the last frost has passed and there is no more danger of sudden cold.
COMPANION PLANTS DO’S AND DON’TS
The traditional “Three Sisters” are corn, beans and squash! It’s best to plant a corn variety that you won’t harvest until later in the season, so that you don’t have to step over (and disturb) growing squashes and beans in order to harvest your corn.
Also, lettuce benefits from the shade of this tall growing plant, and pole beans can climb up the stalks. As well, amaranth makes a great mulch and competes with pesky weeds.
You can also plant sunflowers of a similar height between your corn rows to separate varieties that need isolation from each other.
Want more options? Cucumber, beets, dill, melons, parsley, and potatoes are all good for growing as a companion plant!
Celery doesn’t make a good companion for corn, and neither do tomatoes since they get attacked by the same worm as corn.
GROWING STRUCTURE CONSIDERATIONS
You can grow corn in a container, as long as it’s big enough to allow block planting. This planting process is important so that your corn can have sufficient pollination by wind. The container also needs good water drainage to prevent diseases from growing in too-wet soil.
They should be at least six feet long and four feet wide to provide enough space for block planting.
You will get the most space when you sow your corn directly into the ground. Preferably, the soil will be fertile and evenly watered, as well as free from any pre-existing harmful diseases.
In general, you can prevent diseases and nutritional exhaustion by rotating your crops every 4 years, and also by composting any old stalks.
COMMON PROBLEMS AND THEIR SOLUTIONS
There are a lot of pests, diseases, and nutrient deficiencies that could threaten your corn crop. Not to worry – we’ve listed them below, as well as how to either avoid or fix the problem!
APHIDS: These are pests that feed on the tassels, leaves and ears, and will stunt the growth of young plants. They’re also known to spread a lot of diseases!
LOOPERS: These pests are pale and olive green. They chew into the center of young corn plants, and can actually kill your plants if their growing tip is damaged.
SEED CORN MAGGOT: It attacks germinating seeds and can prevent your plants from growing.
CORN EARWORM: Its larvae feed on the silks and ears of your corn.
CUTWORMS AND ARMYWORMS: Its larvae feed near the soil surface and will damage your plants close to the ground.
RUST: You’ll see rusty orange streaks on leaves that release a powdery substance.
NEMATODE: They feed on the roots and produce galls (swelled growths), which leaves the roots deformed. A heavy nematode infestation can lead to the wilting and death of your corn plants.
DOWNY MILDEW: Two weeks after sowing, this fungus can cause the stunting of your seedlings. Older plants will get lesions and streaking on their leaves, and infected plants will typically seem more rigid and narrow than the healthy ones.
COMMON SMUT:: This fungus causes firm, tumor-like growths on the leaves, stem, ears and tassels of your corn.
MAIZE DWARF MOSAIC VIRUS: Spread by insects, the typical symptom of this virus is a mosaic pattern on the leaves. It can also cause lesions on your corn.
CORN LEAF BLIGHTS: A disease causing lesions to appear that are grey to brown in color and can spread in long veins over the leaves of your corn plants.
SLUGS: These slimy pests leave irregular shaped holes in the leaves and stems of your corn. Leaves can also be shredded, and you’ll most likely notice slime trails on nearby rocks, plants and walkways.
SIGNS OF DEFICIENCIES
Phosphorous deficiency: Your corn’s leaves will have a purple tinge to them.
Nitrogen deficiency: Your corn’s leaves will turn a very pale green.
Potassium deficiency: The leaf margins turn yellow and brown (symptoms progress from the lower leaves to the upper leaves).
Sulfur deficiency: Yellow-colored stripes will appear on younger leaves.
Zinc deficiency: Upper leaves will have broad yellow bands, which will later turn pale brown or grey (symptoms progress from the middle of the leaves outwards)
Ears do not fill to the tips: There are several reasons for this issue! Hot, dry weather during silking and pollination can be a factor, your plants could be growing too close together, you’ve got low soil fertility, or there’s poor natural pollination. To avoid this issue, make sure to keep your soil moist, plant in the recommended spacing, apply fertilizer, and plant in blocks to ensure good pollination.
FUN FACT: Garlic juice extracts help against certain pests like the corn earworm, European corn borer, fall armyworms, flea beetles, and grasshoppers!
HARVESTING YOUR CORN
Corn is ready to be harvested when the silks on top of an ear are brown and dry, when the cob starts drooping, and when the kernels release a milky juice when they are cut.
Depending on the hybrid you’ve planted, you’ll have a certain amount of time to harvest the ears before the sugar in their kernels turn into starch.
On average, you can pick your ears over a 5-7 days period.
The best time to harvest your corn is either early in the morning, or later in the evening when the weather is cool.
To pick the ears, simply hold the stalk below the ear, then twist the tip of the ear towards the ground until it breaks off.
Depending on the variety, though, it can actually stay fresh up to seven days in the refrigerator! Freezing is another option to preserve your corn, if you’d like more long-term storage.
If you have a pressure canner at home, then you can also can your corn!