Humans have been growing corn for centuries, and we aren’t stopping any time soon. However, growing corn successfully requires knowledge of common corn-growing problems.
First, let’s briefly discuss a few stages of how corn grows and matures. Various issues will arise during each. Then, we’ll go through 11 growing problems you might encounter and how to avoid them.
Stages of Corn Growth
Corn plants produce both male and female flowers, meaning they have a monoecious flowering habit in the plant world. If one thing doesn’t go according to plan when getting pollen from the male flowers to the female ones, proper pollination does not occur, and things start to get a little funky.
Until the vegetative stage, when the corn seed is simply in the emergence stage, it only uses energy stored inside the seed.
Ears and tassels develop, lower leaves die, and pollen-loaded tassels mark the end of vegetative growth.
Once a corn seed has emerged and has two fully developed true leaves, it relies on photosynthesis for its energy and nutrients in the soil to continue growing.
During this time, tillers start forming, which look like side shoots near the base of the plant and are the start of the plant’s central stalk. Ears and tassels begin to form on the stalk, the first true leaves wither away, and lower leaves may die off.
No further vegetative growth will occur when the tassels are fully developed and extended. Leaves may continue to grow, but no new ones will form. When silks begin to emerge a few days later, the plant has moved into reproductive stages.
The vegetative stages of corn last for about 60 days, and growth seems rapid during this time.
Did you know? The phrase “Knee-high by the Fourth of July” refers to sweet corn growth and how to judge if your crop is where it should be for a healthy harvest.
Tassels release pollen, which fertilizes ovules through the corn’s silks.
As mentioned above, the first sign of reproductive stages in corn is marked by the emergence of silks. The kernel amount is determined at this point, but the plant must still be pollinated so proper kernel formation can occur. The plant is now shifting its focus on continuing the life of the next generation of corn.
Now, let’s talk about the tassels atop the corn plants. They are the male part of the plant and contain pollen when fully matured. When silks emerge, they catch pollen that falls from tassels, blows by in the wind, or is transferred through insect legs and wings. Within the next 24-36 hours, the pollen moves down into the ovule (the female part of the plant), where pollination occurs.
This is the time of the corn plant life cycle when moisture levels and nutrients are the most important. If silks do not emerge on time or dry up due to low moisture levels, they cannot capture pollen and move it into the ovule for pollination.
Kernel Development and Plant Maturation
If pollination is successful and moisture is sufficient, kernels develop.
If proper pollination occurs and moisture levels are ample, the kernels will develop, filling with moisture and becoming sweet and starchy. Kernels will harden and change from white to yellow. Silks will begin to brown over about three weeks, alerting you that it’s time to harvest.
Pro tip: At this time, you should protect your crop from critters who may want to get their hands on your sweet corn! More on how to do so a bit later.
Now that we’ve had a brief lesson on how corn grows and matures, let’s explore some corn-growing problems you might encounter.
Poor Germination Rate Due to Seed Viability
Purchase seeds from a reputable source and check germination rates before buying.
The first corn-growing problem is a potentially low germination rate. If your seed packet says the germination rate is 85% or above, but you are experiencing a much lower rate, this would be considered a poor germination rate.
Solution: Ensure seeds are viable before sowing. Do this by completing a germination test. Place ten seeds on a wet paper towel, fold it in half, put them in a plastic baggie, and place in a protected, warm place, like atop the fridge. Wait several days, and then count how many seeds have germinated.
This will give you an estimate of your germination rate. While this test does not accurately depict the overall germination rate of all the seeds in your packet, having 9 out of 10 seeds germinate means that 90% of those seeds successfully germinated, indicating a high germination success rate.
Be sure to purchase your seeds from a reputable source and check the germination rates before ordering. In the United States, the USDA has germination rate requirements that most reliable seed companies are required to meet at the time of sale; if they do not meet or exceed those seed germination rates, a reliable seller will not sell that seed lot.
The older your seeds are, the lower their germination rate may be. Remember, your seed is a living thing; inside that seed coat is an embryonic plant. If it is stored for too long, it will exhaust the endosperm of the seed (which acts as the plant’s initial food source) and will die off, making it unable to germinate. If you’re trying to germinate a packet of seeds that you bought three years ago, their germination rate will not be the same as it was when you purchased it!
Pro tip: If no seeds have germinated a week or two after the normal germination time listed on the packet, toss them. They are no good.
Poor Germination Rate Due to Growing Conditions
For direct sowing, ensure the soil is consistently at 50°F to avoid dormancy, pests, and rot issues.
Look for visible signs of germination. If your seeds were viable but few plants germinated, the soil may have been overly cold or damp.
Solution: If you can start seeds indoors or in a heated area, this may yield better germination results. If you can only direct sow in outside soil, be sure the soil has reached 50° and remains at this temperature consistently. Otherwise, the seed will lie dormant and may become vulnerable to pests, rot, or simply not germinate.
Leaves Rolling Inward
Lack of moisture during rapid ear growth can cause inward curling in leaf tissues.
Inadequate moisture levels are another corn-growing problem. When ears are formed, growth is rapid, requiring lots of consistent moisture.
Be sure to keep your eyes on your crop at all stages, but especially during the first 60 days, as a lot of stuff is happening inside. Look for signs the plant may give you that something is amiss.
Solution: Water heavily and often. When the soil is dry about 4 inches down, water again. Heavily mulching your corn plants will help conserve moisture and is highly recommended.
Wireworms are reddish-brown, slender pests that feed on roots and seeds, often damaging newly planted crops.
Pests are a common corn-growing problem. Wireworms are about ½ inch – two inches long, hard-bodied, and very slender. They stand out in the soil due to their bright reddish brown color and whipping body movements. They are the click beetle’s larvae, which is this pest’s adult life cycle. You’ve likely encountered both of them somewhere along your gardening journey.
Wireworms feed on the roots and seeds of newly seeded or transplanted crops. Wireworms may hollow out the seeds when corn is directly sown, resulting in no germination.
Otherwise, they may feed on the roots and stems of young corn plants, resulting in poor performance or crop failure. They are most common in April-June, at the most crucial growth stages of corn, and they stick around longer in cool and wet soil conditions, moving deeper when temperatures warm up.
Solution: Set up a bait station about three weeks before planting out your corn to determine the wireworm levels in the soil and estimate your potential risk for loss. Do this by selecting five or so random test sites in your field. Bury a handful of untreated corn and wheat seeds about 6 inches down, cover it with black plastic to warm the soil, and mark it with a flag for easy identification later. Before transplanting the corn, dig up the seeds and see how much damage occurred.
Seed treatment can be used if low populations are detected. There are also pre-plant insecticides. However, note that there are no treatment options once you have wireworms and there is significant damage. If you replant a field when wireworms are still present, you will likely see the same results.
Cutworms are brown or gray soil-dwelling pests that chew through young plants at night.
If you notice your young plants simply falling over at the soil surface, you might be experiencing the damage of cutworms. These feisty monsters hibernate and hide in the soil, are dull in color, typically brown or gray, and feature small dots along their sides. They curl up when you disturb them, and the larvae can reach up to two inches long.
Cutworms come out at night and chew right through the stems of plants at the soil surface, decapitating your precious crops. Cutworm damage is typically found in the spring, as they like to feed mainly on young plants.
Pro tip: If direct sowing, start a tray or two of seedlings indoors to replace any fallen prey to cutworms. If transplanting, save the extras for the same reason and simply go along your plot and replace any that have been lost.
Solution: Immediately kill cutworms if you see them in your soil. However, remove all debris to prevent them from hanging out in your garden.
You can also place a barrier around your young plants to keep cutworms from reaching them. This could be a physical barrier, such as a toilet paper roll around the plant or a ring of diatomaceous earth powder, coffee grounds, or egg shells. Be sure to reapply after each rainfall.
Furthermore, you could interplant sage, tansy, and thyme, as these strong-scented herbs repel cutworms.
Use insect netting, reflective items, or scare tactics like scare tape and scarecrows to deter birds.
If you conquer the pests, local wildlife is the next potential corn-growing problem. Birds love young corn plants and may swoop in and snatch them right out of the ground when plants are just emerging or newly transplanted. Corn is one of the crow’s favorite things to snack on, so watch out for them.
Solution: Insect netting can be used to protect young, vulnerable plants. Just be sure to hoop and cover soon after germination if you directly sow or right after your transplant. You can also use scare tape, reflective items such as pinwheels, or post up a scarecrow to give them a run for their money, er, corn.
Raccoons and Other Critters
Corn ripens quickly, attracting raccoons, deer, and turkeys.
Corn goes from being almost ready to ready very quickly, and you may not be the only one waiting for the perfect time to harvest. Somehow, raccoons, deer, and even wild turkeys know when sweet corn is ripe and can destroy a whole crop overnight or in a daytime pass by.
Solution: Raccoons come out and wreak havoc at night and spook easily by humans and loud noises. A few things that may scare them off:
- Try hanging tin pans from a tall post in the ground near your corn and allow them to blow around in the wind. Wind chimes work as well.
- Plug a radio in nearby and play it overnight. Change the radio station often so it doesn’t become just background noise to the animals you hope to deter.
- Sprinkle blood meal around your corn plot. They’ll think a predator is lurking nearby and should avoid the area.
- Motion-activated lights or sound.
- Make a DIY deterrent by mixing cayenne pepper and blended garlic into a gallon of water and a teaspoon of soap. Spray or pour around your plot. Cinnamon is also believed to confuse raccoons’ sense of smell, so you could try adding that to the mix or sprinkling it on or around your plants.
- If all else fails, you can install a temporary electric fence when your corn is about to ripen—no need to have it on during the earlier stages.
Northern Leaf Corn Blight
This fungus favors warm temperatures and humidity and causes lesions on leaves.
Northern Leaf Corn Blight (NLCB) is caused by the fungus Setosphaeria turcicum (synonym Exserohilum turcicum), which favors temperatures between 65-80° and high humidity levels, making it one of the main diseases striking corn in states like Florida in the spring and across the Midwest in mid-late summer.
Lesions caused by NLCB are gray to brown, can be up to six inches long, and can appear water-soaked. The spots begin on lower husk leaves first, work their way up, and darken when the fungus is sporulating. The length, size, and color of the spots depend on the variety and age of the corn. Significant loss can occur if this disease is contracted before the corn silks.
There are many types of delicious corn varieties to choose from. Try growing ‘Honey and Cream’ sweet corn for a delicious option resistant to common rust and Northern leaf blight.
Southern Leaf Corn Blight
This blight is caused by a warm-temperature-loving fungus that damages young seedlings.
Southern Leaf Corn Blight (SLCB) is caused by the fungus Bipolaris maydis, which favors warmer temperatures between 68-90°. States like Georgia and Florida usually encounter SLCB in the fall.
Symptoms of SLCB include small yellow halos surrounding up to one-inch lesions and can destroy young seedlings if not caught in time.
Solution: Strobilurin and sterol-inhibiting fungicides can be used preventatively but will only be effective if applied when the time is right, before extreme infection. Disease-resistant varieties exist, and deep tillage can also work for prevention. If you practice no-till methods, at least a two-year crop rotation plan is recommended.
General Plant Issues
If small ears form despite healthy stalks, nutrient deficiency might be the issue.
If your stalks look healthy but the ears being produced are all relatively small, they may not have had the nutrients they needed to form proper-sized ears.
Solution: Space corn plants nine to 12 inches apart in a row of two per variety to allow for proper pollination. Any less than nine inches will not allow them to grow outward enough, receive ample airflow, or cause them to run short on nutrients when it comes time to mature the corn ears.
Pro tip: Try adding a well-balanced fertilizer alongside your corn plot about a month after they are transplanted and again mid-season to ensure they have what they need to form nice, full cobs.
Incomplete or Delayed Silk Emergence
Incomplete silk emergence can result from low moisture levels, leading to poor pollination.
This might not sound like a huge deal, but the corn plant transitions into reproductive stages when the silks emerge from the husks. Each silk represents a female flower of the plant. Each one being pollinated leads to a kernel of corn.
The most common occurrence that can cause incomplete silk emergence is severe drought conditions. Silks are highly sensitive to moisture levels because they need the highest water content of any other corn plant tissue. When low moisture levels are present, silks emerge more slowly or fail to do so at all.
If “silking” is delayed too long or fails to happen at all, little pollination or none at all occurs because most or all of the pollen has already been shed, leading to an underdeveloped corn cob that offers few or no kernels, also known as blanks.
Solution: Water regularly and mulch heavily to hold in that moisture.
Tips For Success
Check corn cobs for ripe kernels when silks brown and leaves dry up.
Corn performs best when grown in well-draining soil full of organic matter that receives full sun. It will perform best when planted in blocks or short rows of four spaced 15 inches apart.
Block planting works best due to its ability to pollinate others in the block due to their proximity to each other. Pollen can easily drift over to a corn friend when the wind blows. Likewise, when bees find your block, they’ll fly from one corn plant to the next easily.
Delay planting until the soil temperature is at least 62-65°. Don’t rush it! Starting corn indoors is recommended for a head start or during a cool spring. Mulch plants heavily and water 1-2 inches per week.
Side dressing with composted manure or a general fertilizer is a good idea, as corn is a heavy feeder. This can be done about a month after being transplanted, and they are well established, and again when you see tassels start to form. They need ample nutrients to produce healthy, beautiful corn cobs.
Start checking the tips of your corn cobs for fully formed kernels about three weeks after you start seeing silks. The leaves will dry up, and the silks will brown when corn is ripe. The juice from a kernel should be milky white when ripe and ready to be harvested.
Pro tip: If you have an abundance of fresh corn and can’t possibly eat any more, try cutting it off the cob and freezing it on a cookie sheet. Once completely frozen, store them in a freezer-safe bag for up to 12 months. Use it in soups, chowders, and dips all winter long.
There is nothing like homegrown, sweet corn fresh off the stalk, so it’s absolutely worth growing. Just be aware of these issues that might arise, plan accordingly, and enjoy fresh corn all season long!