How To Grow Organic Corn?
INTERESTING CORN FACTS
- Throughout much of the world, corn is known as Maize (sounds like mays). The Aztecs and Mayans (S. America) were growing corn well before it made it’s way to Europe in the 15th century.
- In N. America, commercial farmers favor growing corn over any other crop by around double.
- One of the oldest forms of corn is popcorn. Popcorn that was found in New Mexico and has been dated to around 3600 B.C.
- Sweet corn is eaten as a vegetable most often (think “corn-on-the-cob), while Field Corn is typically what is grown commercially for animal feed and ethanol.
WHEN TO PLANT
- You can start planting and growing sweet corn about a week after the last frost or when the soil temperature is about 60°F.
- In colder areas, you can warm the soil by placing plastic over your planting area at least a week before planting. Use dirt around the edges to keep plastic in place.
- Most varieties of corn will not germinate if soil temperature is below 50°F.
- If planted too early, you may end up with spindly, deformed stalks or risk your seedlings being killed if a frost occurs.
- Here in the North, we wait until the end of May and when the weather is on a warming trend; at least 70°F air temperature in the day and no lower than 50°F at night).
- In the South, corn can be planted as early as February or March if weather conditions are right.
- If the ground is still really wet, wait to plant. Corn seed sown in cold, moist soil is susceptible to fungal disease.
- Pre-sprouting seeds is recommended in Northern climates as it increases germination as much as 50% in our experience.
- If you live in an area with a short growing season, you might also want to consider growing an early-maturing, short-season hybrid. Hybrids are not recommended though if you are planning to save seeds.
- Cross-pollination of different varieties can cause tough, starchy kernels. Because of this, we recommend planting only one variety.
- What if you want a longer corn harvest? Rather than planting early, mid-season, and late varieties and risking starchy kernels, we recommend planting your favorite variety every 2 weeks or when three to four leaves have appeared on the seedlings in the previous planting.
- You can continue re-planting up to 6 weeks.
WHERE TO PLANT
- Plant your corn in full sun with some protection from the wind if possible.
- Plant corn in the North side of the garden so the tall corn plants won’t shade out the rest of your garden.
- Alternately, if you have plants that need partial shade during the hotter parts of the summer, position your corn to protect those crops from too much sun.
- Corn is a heavy nitrogen feeder, so it will thrive in an area where nitrogen-fixing plants such as beans, peas, clover, or alfalfa grew the previous season.
PREPARING YOUR SOIL
- Soil nutrient levels must be optimum for plant and kernel development, disease resistance, flavor, and nutrition.
- Sweet corn thrives best in deep, naturally rich, and easily worked soil with plenty of organic matter. However, any well-drained soil is suitable. Sandy soils are best for early crops since sandy soils warm up faster in the spring than heavy soils.
- Preparation for next year’s corn planting begins in the fall by firstplanting a cover crop of legumes or alfalfa for nitrogen-fixing; spade or rototill in your cover crop in the spring.
- Compared to other crops, corn is a moderate to heavy consumer of most nutrients, especially nitrogen.
- Loosen the soil about 6 inches deep, using a spade or garden fork. Break up the clods to insure good contact between the soil and the seed.
- Add generous amounts of composted manure, compost and if necessary, lime; 1# of lime per 100 sq.ft. should be sufficient.
- Generally, compost and/or chicken and cow manures (well-composted, not fresh) have their strongest effect on the corn crop if applied just in advance of planting; use 20 to 30 lbs. per 100 sq.ft.
- Increase phosphorus levels with bone meal or blood meal; these should be added during planting for direct contact with the corn’s roots.
- Optimal pH levels for growing corn are 6.0 to 6.5.
CHOOSING THE RIGHT SEED VARIETIES
- Standard sweet corn varieties offer traditional flavor and grow better in lower soil temperatures than the varieties below, but their sugar turns to starch quickly after harvest.
- Sugar-enhanced varieties are sweeter and more tender than standard varieties, and super-sweets are the sweetest of all but are less vigorous than other hybrids and need moist, warm soil to grow well.
- If you live in an area with a short growing season, you might want to consider growing an early-maturing, short season hybrid. Hybrids are not recommended though if you are planning to save seeds.
SEEDS AND GERMINATION
- Sweet corn requires warm soil for germination; minimum of 55°F for standard sweet corn varieties and about 65°F for super sweet varieties.
- The best germination temperatures, however, are between 75° – 85°F; at these temperatures, corn seeds germinate in 3 to 4 days.
- It’s best to wait until your soil temperature has reached a steady 60°F or above (70°F for super-sweet corn) before planting to get the best germination results.
- For more rapid germination, warm the soil by covering the planting area with plastic 10-14 days sowing
- In cooler climates (like where we live), it is best to pre-sprout your corn seeds in a warm place (we do it in the kitchen).
- Determine how many seeds you’ll need for the area you want to plant, soak the seeds in water, then place them in a jar or cup, then cover the seeds with a water-soaked rag or washcloth; rinse once or twice daily until the seeds have sprouted.
- At 70°F in our home, the seeds sprout in about 3 to 4 days.
- Once most of the seeds are sprouted, plant them in your garden immediately or the sprouts will get too long and break off easily.
- Once you’ve purchased corn seeds, they should be good for 2 years.
GETTING STARTED INDOORS (and transplanting)
- Planting corn indoors is not a best practice as corn doesn’t transplant well, plus it grows very quickly in your garden; we consider it wasted effort. However, if you believe you must plant indoors, plant in individual 4″ peat pots. When transplanting, make sure not to disturb the roots or the plant will die. Dig a hole, place the entire peat pot in the hole and back-fill the dirt to the collar of the corn plant (at the same level as it is in the peat pot).
PLANTING CORN SEED DIRECTLY IN YOUR GARDEN
- Planting Basics: seed depth: approx. 2″ (3″ in sandy soil) – seed spacing: 3″ to 4″ (we like to over-plant and thin our corn to 8″ to 12″ apart) – row width: 30″to 36″ (I like to plant rows 36″ apart so I can get my Troybilt Horse Tiller “Attiller the Hun” between the rows).
- It’s important not to crowd your plants as the corn ears will be smaller (or not form at all).
- Corn is wind-pollinated, so plant four or more short rows of sweet corn side-by-side rather than one or two long rows. This will help insure good pollination and ear development. Inadequate pollination results in poorly-filled ears.
- Cross-pollination of different varieties can cause tough, starchy kernels.
- To prevent corn from cross-pollinating, corn varieties must be planted at least 250 feet from white varieties and 500 feet or more from other colored varieties.
- Note: most of us don’t have that much space or we have neighbors close by growing corn, so it can be difficult to isolate different corn varieties by distance. If you’re on good terms with your gardening neighbors, you might see if you can match varieties.
- So, what do you do if you want a longer corn harvest? Rather than planting early, mid-season, and late varieties and risking starchy kernels, we recommend you plant your favorite variety every 2 weeks (or when three to four leaves have appeared on the seedlings in the previous planting.
- You can continue re-planting up to 6 weeks.
- We’ve been asked how much corn to plant per person in your household – we estimate about 15 plants per person for fresh sweet corn.
- If you want to can and/or freeze corn, add another 30 or more plants per person.
- We’ve experimented with planting corn in raised rows, but found that with corn’s shallow root system, a good rain can easily wash away the soil and expose the roots, leaving us to mound more soil at the base of the plant every time we got a good rain. So, traditionally, we have preferred good ol’ row planting. But, this year, we are excited to give Three Sisters Planting a try. This is an ancient method of planting that puts three different vegetable plants together to compliment each other in a number of ways. If you would like to learn more about this planting method, please see this article on Three Sisters Planting.
- Jenny’s Tip #1: This past year we discovered a liquid organic leaf spray fertilizer (you spray your plants every two weeks) called Organic Garden Miracle™ that naturally stimulates your garden plants to create more plant sugar. Plant sugar is what makes your plants strong, produce flowers and fruit, and controls the flavor, sweetness, quantity, and size of fruits your plant produces. And it has a risk-free guarantee that made us very comfortable trying it.
- When the corn seedlings are 3-6” inches tall, thin to one plant per 8 to 12 inches, by cutting the unwanted seedlings at soil level or pulling them up if they’re not too close together.
- Hand-pollinating: If you want to help your plants form full ears of corn, hand-pollinating is one way to do it; this ensures that each ear fills out completely.
- To pollinate, grab the tassels and shake them to distribute the pollen to the silks below.
- Another method is to gently shake the tassels into a small paper bag, collecting the pollen, then sprinkle the pollen onto the emerging silks, repeating once or twice over the next few days. This method takes a little more time but works very well.
- Some sweet corn varieties produce more side shoots or “suckers” than others. Removing these side shoots is time consuming and does not improve yields.
- Side-dress the stalks with a nitrogen-rich fertilizer (such as well-composted animal manure) when plants have 8-10 leaves, then again when tassels appear.
- Mulching: hill soil mixed with compost around the base of the plant when they are 6” high. This will help to anchor the plants and keep the roots covered and cool.
- Weeding: If you use a rototiller like I do, keep at least 6″ from your plant’s base. Hand-pull any weeds that are closer, and if they’re too big and too close to the base of your plants, especially if they’re small, cut them off rather than pulling them
- Although corn is a warm-weather crop, a lack of water at critical periods can seriously affect development of the ears and reduce yield.
- If rainfall is sparse, be sure to water your crop thoroughly (1 to 1.5 inches per week) when the tassels emerge, and when the ears and silk appears.
- Push your finger into the soil to check for moisture. If you feel the soil dry more than 1” down, the plants need watered.
- Sandy soils may require more frequent watering.
- The roots of the Corn plant are located close to the stalks. It is also a very shallow root system, therefore when watering, place the water source near the base of each stalk to be sure the roots are able to absorb the water.
- If you grow squash amidst the corn hills, its leaves will act as a living mulch, but it will also compete with the corn for moisture, so soak the soil well when you water and check moisture levels more frequently. See article on Three Sisters Planting.
- A sign of over-watering is when leaves turn pale green or yellow and then fall off, the plants grow poorly, and spindly stems begin to flop over. Stop watering until the plants return to normal health.
- Drip irrigation applies even moisture to the soil; overhead watering can wash pollen off corn plants
COMPANION PLANTING / ROTATION
- Plant corn together with pole beans and vine crops like cucumbers, squash, and pumpkins. See the “Three Sisters Planting” article on our Resources page.
- Pole beans and vine crops planted on the sunny side of a row of corn will grow up the stalks, and provide stability for both plants.
- Pigweed thistle raises nutrients from the subsoil to where the corn can reach them.
- Keep corn at least 20 feet from tomato plants; tomatoes and corn are attacked by the same worm.
- Corn is a heavy feeder; legumes (beans, peas) fix nitrogen from air into the soil when they begin to die back. However, they do not feed the corn while it is growing.
- Legumes must be planted as a cover crop the previous season in the same location to benefit this year’s corn.
- Check your stalks when the silks are brown and damp by poking a fingernail into a kernel – it’s ready when the liquid that squirts out is milky. This stage occurs about 18 to 24 days after the appearance of the first silk strands.
- Sweet corn remains in the milk stage less than a week.
- Signs that indicate the corn is ready for harvest are: drying and browning of the silks, fullness of the tip kernels, and firmness of the un-husked ears.
- To harvest your corn, snap off the ears by hand with a quick but firm downward push, twist and pull. Hold the stalk with the other hand just above where the ear attaches to the stalk to prevent it from breaking.
- In warmer temperatures, the sugar in sweet corn quickly decreases and the starch increases, making the flavor bland; the ears should be eaten, processed or refrigerated as soon as possible.
- Cut or pull out the cornstalks immediately after harvest and put them in a compost pile.
- Cut the stalks in one foot lengths or shred them to help speed up the composting process.
- A pile of cornstalks left alone over winter will only be a pile of woody stalks in the spring.
- For preservation of flavor and sugar content corn must be brought to 40°F within 1 hour from harvest or the sugars quickly begin to turn to starch.
- The quickest way to accomplish this is to give the corn an ice bath.
- Corn only preserves well for about 1 week in the refrigerator; after picking, use the sweet corn immediately for fresh eating, canning, freezing, or dehydrating.
- Freezing sweet corn is the best way to preserve the taste of corn (we’ll be putting instructions on this site soon for how to do this).
PREVENTATIVE AND NATURAL SOLUTIONS TO COMMON PESTS AND PROBLEMS
- PESTS: The most widespread pests are European corn borers and corn earworms.
- Corn Borers: Corn borers are fleshed-colored worms, about 1” in length with tiny black spots. Once inside the plant, they are difficult to control.
- European corn borers attack the stalk just below the tassels. Look for small holes with sawdust-like material near the opening. Squeeze the stalk to destroy the borer.
- Prevention – Timing: by planting a week or two after the soil warms you can avoid the time the borers emerge in the spring.
- Prevention – Other: preventative care such as the use of row covers or milder natural sprays in early stages, such as neem or pyrethrins to avoid having severe infestations.
- Treatment – Handpicking: for small gardens hand-picking the larvae off the corn silk may work.
- Treatment – Organic: Bt (Bacillus thuringiensis) is an effective option for organic control of a medium infestation; granular Bt seems to work best.
- Bt can also be used by mixing with vegetable oil and then applying it on the corn silk 2-3 days after the silk has matured. This is effective, but Bt is only effective for between 3 and 7 days, then it must be reapplied.
- Treatment – Non-organic: Rotenone can be used as a very last resort in severe infestations but it is not recommended for organic gardening due to it’s natural toxicity and harm to beneficial insects.
- Corn Earworms: Corn earworms attack the tips of the ears when the plants begin to tassel. If the damage is minor, you can cut off the tips of the ears after harvesting.
- Corn earworm larvae vary greatly in color ranging in from light green or pink to dark brown or nearly black. They have alternating light and dark stripes running the length of the body. Double dark stripes can usually be seen down the center of the back and the underside of the larva is typically light-colored.
- Prevention – Corn Variety: The best way to prevent corn earworm infestations is to choose a corn variety that is resistant to this pest due to its tight husk.
- Another preventative method is to spray a small amount of a 20-to-1 mix of Bt (Bacillus thuringiensis) and mineral oil to the silk at the ear tip just as the silk begins to wilt.
- Animal Pests: If your corn patch is small and critters (such as raccoons or birds) are invading your ears, try wrapping duct tape around each ear an inch above the stalk and an inch below the tip to prevent access inside.
- If your crop is larger, using an electric fence of two or three wires spaced 4” apart and starting 4” off the ground will help detour these pests. Be sure to have the fence set up before the corn is ripe; raccoons prefer corn in the early stages of ripeness.
- If you have a dog, kenneling the dog near the corn can also help to keep animal pests away.
- Dry spells can cause leaf damage. During dry periods, mist the leaves a couple times a week with a sprinkler set on the mist setting.
- If the ends of the leaves have dried up, cut them off with some clean scissors just at the end of the dry area without cutting into the healthy part.
- Disease – Corn Smut: is a fungus which can infect the plant through wounds caused by cultivation, hail, or insects.
- It can also infect newly developed silks. It is an abnormal greenish-white outgrowth, filled with black spores. Although considered a delicacy in authentic Mexican and some Chinese cooking, Americans generally do not find it appetizing.
- No hybrid seed is completely immune to smut, but most of the resistant varieties will prevent this disease in your corn crop.
- Many of the commonly used sweet corn varieties are susceptible to Corn Smut disease.
- However, the White Sugary Enhancer varieties are more resistant to smut than either the White or Bi-color Super-sweet varieties.
- Years with warm and dry early summers, followed by rainy weather have a greater risk of smut disease developing in corn crops.
- Prevention: Do not over-apply nitrogen-heavy compost. Soils too high in nitrogen have been shown to increase the risk of disease.
- Treatment: To control the fungus, remove any galls before the dark spores form inside. Burn or bag and throw away the diseased plant parts to prevent spreading the disease.
- Keep an eye on this subject…we’ve got lots of information coming soon!