Sweet Corn Planting Guide

How to Grow Sweet Corn

Fresh home grown sweet corn, straight off the stalk is undeniably the best you’ll ever taste. Utilizing simple time-tested techniques, you can use a limited garden space effectively to grow an abundance of this classic American staple crop .


USDA Zones 3 – 11

Botanical Name: Zea Mays

Full Sun

Fertilizer: High Nitrogen

Soil pH 5.5 to 7.0

Sweet corn can be divided into three major groups. Standard, Normal sugary, Sugar-enhanced and Super sweet

Standard sweet corn varieties have a traditional flavor, and germinate better in colder Northern soils . Unfortunately their sugar rapidly turns to starch shortly after harvest which makes this an unpopular variety among Commercial growers.

For home growers in Colder areas who plan on eating it straight off the plant it is a good choice. Sugar-enhanced varieties are more tender and sweeter than standard, and naturally supersweets are the sweetest , but are not as vigorous as other hybrid sweet corn, they also require moist, warm soil and more careful cultivation to grow well. All varieties are available as white, yellow, or bi-colored, the color is strictly a matter of aesthetic choice. See Also: Unusual Corn Varieties

Many garden gurus recommend early mid and late season plantings of corn in order to ensure a steady supply. I generally prefer to plant a modest amount once weekly after my initial large early spring planting I culminate the season about 4 – 5 weeks before the first frost of Autumn – occasionally I lose some of the last planting this way , but not enough to be overly concerned with.

A good rule of thumb is to sow three seeds for each plant you anticipate growing, then thin to the strongest seedlings, corn’s germination rate is generally around 75 to 80 percent.

Search for varieties resistant to pests and diseases known in your area . Try to avoid planting different varieties of corn in close proximity to one another, as cross pollination leads to tough, starchy kernels.

Soil Preparation

Corn has shallow roots, and uses a lot of nitrogen as well as trace elements, it is a heavy feeder.

To help your crop get off to the best start possible, prepare the soil first with a nitrogen-rich fertilizer. Well rotted manure or compost is also helpful. Dig in a well rotted manure and compost about a week or two before planting day. It’s also a good idea to sprinkle a modest amount of food grade diatomaceous earthCorn Soil Preperation diatomaceous earth over the seeds when planting, as this will help prevent future pest problems.

Site Selection

Plant in the northern side of the garden as corn stalks will deny sunlight to the rest of your garden crops ,you also might want to grow some where it will provide shade to plants that can not tolerate full sunlight. As stated earlier in this article- do not plant different varieties of corn together


Corn , unlike most other vegetables does not rely on insects for pollination, it is wind-pollinated. Because of this a square plot is much more effective than planting in extended rows and also uses your garden space more efficiently. Even in a small garden, a square formation ensures proper wind pollination no matter which way the wind blows.

Planting ~ Transplanting ~ Starting Seeds Indoors

Corn seed sown in cold, moist soil is much more susceptible to fungal diseases. Corn germinates quickly in soil that’s over 60oF. Starting seeds indoors is advisable in most regions especially if you have a short growing season. I generally have several trays of seed in the germination process going at any particular time during the growing season and stop planting more seedlings indoors about 6 weeks before the first Autumn frost for transplant outdoors 4 – 5 weeks before the first frost of Autumn . You also want to keep in mind that corn doesn’t always transplant well- so expect to lose a few stalks in the transplant process.

Types of Sweet Corn

Sweet corn can be divided into 2 primary categories. Open Pollinated and Hybrid.

Open Pollinated (OP) are the heirloom varieties with a long history, they were very popular in the early 1900s and late 1800s and are becoming increasingly popular today. These varieties tend to be less sweet than the modern hybrid varieties. Their sugars turn to starch rapidly after harvesting, so they need to be cooked right after harvesting to preserve the flavor.

Hybrids are the result of breeding two distinct varieties . The offspring of such a mating produces a new variety of the same species that incorporates certain desirable characteristics of both parents. Another way that seed can be hybridized is by genetic modification. Often referred to as GM or GMO seed {Genetically Modified Organism} . Despite it’s unpopularity with the Organic Gardening Community hybrid corn does produce dramatically higher yields.

Standard and Normal sugary [su]

A variety with this designation produces kernels containing moderate but varying degrees of sugar. The overall sugar content depends on the variety, but in general “su” varieties accumulate two times more sugar than standard field corn.

They are mildly sweet and are generally more tolerant of cooler climates. They convert their sugars into starch shortly after harvest and should be cooked as soon as possible. These corns are also referred to as normal sugary hybrids, standard hybrids and regular sweet hybrids. They germinate better in cold soils than other varieties.

Sugar-enhanced [se] [se+]

Varieties with this designation contain more sugars . On average, “se” varieties, when refrigerated, will remain sweeter for two to four days from harvest. Also referred to as sugary enhanced hybrids, , SE varieties are a good choice for the backyard gardener or novice. These hybrids offer gardeners a greater window for harvesting before losing their sweet flavor and don’t need to be kept isolated from other varieties. See: Isolating Corn

Supersweet [sh2]

An important thing to remember when planting super sweets is to distance them at least 300 feet from other types of sweet corn plantings. The corn will cross-pollinate and produce starchy kernels.

You might notice that the seeds of super sweets are collapsed and wrinkled – shriveled (hence the sh designation) This is because they contain minimal starch. This gives them the sweetest flavor of all corn varieties and allows them to maintain their flavor for up to 10 days after being harvested. Super Sweets varieties are best suited for the more experienced gardener. They need to be isolated from other varieties to prevent cross pollination which turns corn tough and starchy , the seeds are also more prone to rotting before germinating in wet soil.

Related: How to Grow Hydroponic Sweet Corn

Companion Planting

Plant corn together with pole beans and vine crops such as squash, and smaller varieties of pumpkins which makes for a good companion scheme. The beans fix nitrogen into the soil which the corn thrives on, and the squash will benefit from the corn stalks and fertile soil as well.

Planting squash amidst the corn will also act as a living mulch, but will compete with the corn for moisture, so soak the soil well.

See: Corn Companion Plants

After planting, watering is an important concern, especially during pollination. If corn suffers a drought at this time, you’ll end up with only a few measly kernels per cob.Drip irrigation or a soaker hose is advisable to get the water directly to the plants roots. Mulch such as straw or grass clippings between the stalks helps keep the soil moist. Side dress the stalks with a nitrogen-rich fertilizer a month after planting your then again when baby corns appear.

The most common pest of corn is the Corn Ear Worm. They will easily destroy your harvest. Should you notice worms or worm silk on your plants. Spray them with Bacillius thuringiensis. Reapply weekly or in the event of rain.


There are a number of signs which indicate when to harvest your corn

Harvest 18 to 21 days after the silk first appears.

Harvest when the female silk turns from pale yellow to dark brown.

The angle of the cob changes from being straight to around 30 degrees from the stalk.

And finally you can peel back the husks for a peak. If the kernels look juicy stick a thumb nail in. The kernel will ooze a milky substance, somewhat like that in canned corn if it is ready for harvest.

Grab the stalk and pull the cob down. You’ll hear the cob break away from the stalk. Once your corn stalks begin to yellow the plants life cycle is approaching an end. So harvest the remaining cobs. Some might be underdeveloped while others might be picked in the nick of time. I at times have harvested “Baby Corn” which is tasty cob and all, not all varieties are suitable for this.

See: Why Corn Stalk Leaves Turn Red