Growing Sweet Corn in the Home Garden

Sweet corn is one of our most popular vegetables. An excellent summer treat, sweet corn may also be canned or frozen for year round use. 


Growing Conditions  |  Planting  |  Types & Recommended Cultivars  |  Harvesting & Storing  |  More Information


Growing Conditions

Sweet corn performs best in full sun and fertile, well-drained soils with a pH between 6.0 and 6.5. 

Planting corn seed By SUPER FOX AdobeStock
Plant sweet corn seeds 8 to 12 inches apart in rows 2½ to 3 feet apart. (1)

Planting Sweet Corn

When to Plant

Many gardeners want to plant sweet corn as early as possible to get an early summer harvest. However, when planted too early in the season, soil temperatures can be too low to promote good, consistent germination, increasing the risk of seed rot in cold, wet soil. Most seeds are treated to help prevent rot and will be dyed pink to indicate that they’ve been treated.

Some types of sweet corn more readily germinate and grow in colder soil temperatures and can be planted earlier than others. Standard sweet corn (su) cultivars can be planted in late April in central Iowa (a little earlier in southern Iowa and a little later in northern Iowa). It is recommended that sugar enhanced (se) and synergistic (syn) cultivars be planted one week later than standard sweet corn cultivars. In general, supersweet (sh2) and augmented supersweets (shA/aug) cultivars are the least tolerant of cold soil temperatures. As a result, these cultivars should be planted later than other types (mid-May in central Iowa).

For a continuous supply of sweet corn, plant early, mid-season and late cultivars. Alternatively, the same cultivar can be planted in blocks every two weeks. The last practical planting date for early cultivars is July 1.

How to Plant

Plant only fresh seeds, as planting old seeds will likely result in poor germination and irregular plant stands. Sweet corn performs best in full sun and fertile, well-drained soils with a pH between 6.0 and 6.5. Sow seed at a depth of 1 inch in heavy soils. In light sandy soils, the planting depth can be 2 inches. Space seeds 8 to 12 inches apart in rows 2½ to 3 feet apart. Sweet corn may also be planted in "hills." Sow 4 to 5 seeds per hill with approximately 3 inches between seeds. Hills should be spaced 2½ feet apart with 2½ to 3 feet between rows.

watering young corn By SUPER FOX AdobeStock
Provide adequate water and fertilizer to get good yields. (2) 

Sweet corn requires high levels of nitrogen and moderate amounts of phosphorus and potassium to grow well. Prior to planting, incorporate 2 to 3 pounds of fertilizer per 100 square feet by spreading an all-purpose fertilizer, such as 10-10-10, uniformly over the area and incorporating it into the top 3-4 inches of soil.

Expected Yields

Plants typically produce one good ear of corn per stalk and at least one secondary ear that is usually smaller and lower in quality. When good management practices are applied, such as adequate fertilization and applying approximately 1 inch of water (either from rainfall or irrigation) per week and controlling weeds, the expected yield should be 11 to 13 ears per 10-foot row.

Pollination

Sweet corn is wind pollinated. To insure good pollination and ear development, plant several short rows or blocks rather than 1 or 2 long rows. Inadequate pollination results in poorly filled ears. 

rows of corn By CoreyOHara AdobeStock
Plant sweet corn in blocks instead of long rows to get good pollination. (3)

Cross-Pollination and Isolation

Sweet corn should be isolated from popcorn and field corn to prevent cross-pollination, since the quality of sweet corn will be lowered if it’s cross-pollinated by other types of corn. For example, sweet corn pollinated by popcorn will be tough and starchy.

Different types of sweet corn should also be isolated from each other to prevent cross-pollination, which can lower the quality of the sweet corn. In particular, supersweet and augmented supersweet cultivars should be isolated from standard, sugary enhanced and synergistic sweet corn types. Additionally, isolate sugary enhanced cultivars from standard and synergistic cultivars.

Furthermore, cross pollination from different colors of sweet corn can decrease color purity in the kernels. White kernel cultivars will develop yellow kernels if pollinated by yellow or bi-color corn, and pollen from yellow corn will lead to extra yellow kernels in bi-color cultivars. Pollen from white corn will not affect yellow or bi-color cultivars.

Isolation can be achieved by planting different types at least 250 feet apart; however, this is not a practical option for most home gardeners due to limited space. Another option is to stagger planting dates or select cultivars that mature at different times. A minimum of 14 days should separate the tasseling time of different corn types.

Types of Sweet Corn

Home gardeners can choose from numerous sweet corn varieties. Sweet corn varieties differ in color (yellow, white, bicolor), sugar content, texture, ear size, days to harvest, and other characteristics. 

There are five main types of sweet corn available to home gardeners. These types vary in sugar content, texture, length of harvest period, storage life, seed vigor and germination requirements. The five main types of sweet corn are standard sugary (su), sugary enhanced (se), supersweets (sh2), synergistic (syn) and augmented supersweets (shA or aug). Within each of these major types are cultivars that will ripen in the early, mid and late seasons.

sweet corn photo by Cindy Haynes
There are several types of sweet corn avialble that differ in sugar levels, firmness, and storage life, among other things. (4)

Standard sugary

Standard sugary (su) cultivars have been grown for many years. These cultivars have the traditional sweet corn flavor and texture. Sugar levels are generally between 10 and 15 percent at harvest. Unfortunately, ears of sugary cultivars retain their high quality for only 1 or 2 days. Also, standard sweet corn cultivars don’t store well as sugars quickly convert to starch after harvest. Seeds germinate well at soil temperatures of 55 to 60°F. Suggested standard sweet corn varieties for home gardens in Iowa include:

  • 'Early Sunglow' (yellow)
  • 'Silver Queen' (white)

Sugary enhanced

Sugary enhanced (se) cultivars contain the sugary enhanced gene that produces ears with sweet, tender kernels. Compared to su cultivars, sugar levels of se types are higher and the storage life is 1 to 2 days longer. Seeds germinate well at soil temperature of 55 to 60°F. Suggested sugar-enhanced varieties for home gardens include:

  • 'Bodacious' (yellow)
  • 'Incredible' (yellow)
  • 'Legend' (yellow)
  • 'Luscious' (bicolor)
  • 'Precious Gem' (bicolor)
  • 'Silver King' (white)

Supersweet

Supersweet (sh2) cultivars contain the shrunken-2 gene. These cultivars have very high sugar levels, and convert sugar to starch slowly, allowing for a longer harvest period and a storage life for up to one week with refrigeration. The seedcoats on kernels are rather thick, giving the corn a firmer, crunchy texture. Soil temperatures need to be at least 60°F for optimal germination. Supersweet sweet corn varieites include: 

  • 'Honey 'N Pearl' (bicolor)
  • 'How Sweet It Is' (white)
  • 'Northern Xtra Sweet' (yellow)

Synergistic

Synergistic sweet corn varieties combine the desirable traits of standard, sugar-enhanced, and supersweet varieties.  Synergistic sweet corn varieties are sweet, creamy, and tender with an excellent storage life. Seeds germinate well at soil temperature of 55 to 60°F. Synergistic sweet corn varieties include:

  • 'Providence' (bicolor)
  • 'Montauk' (bicolor)
  • 'Applause' (yellow)
  • 'Innovation' (yellow)
  • 'Mattapoisett' (white)

Augmented supersweets

Augmented supersweet sweet corn varieties are supersweet types that also have the se trait in all their kernels. These varieties are sweet, tender, and have a long harvest period with excellent storage life. Soil temperatures should be at least 60°F for optimal germination. Augmented supersweet varieties include those sold under the brands:

  • Gourmet Sweet™
  • Xtra-Tender™
  • Mirai™

Harvesting and Storing Sweet Corn

Husking sweet corn By Elena_Alex/AdobeStock
Harvest sweet corn when the soft kernels produce a milky juice when punctured with a thumbnail  (5)

Harvesting sweet corn at the proper stage of maturity is essential to ensure a high-quality crop.

Sweet corn should be harvested at the milk stage. At this stage, the silks are brown and dry at the ear tip. When punctured with a thumbnail, the soft kernels produce a milky juice. Overmature sweet corn is tough and doughy. An immature ear is not completely filled to the tip, and the kernels produce a clear, watery liquid when punctured.

The harvest date can be estimated by noting the date of silk emergence. The number of days from silk emergence to harvest is approximately 18 to 23 days. Prime maturity, however, may be reached in 15 days or less if day and night temperatures are exceptionally warm. Most hybrid sweet corn varieties produce two ears per plant. The upper ear usually matures 1 or 2 days before the lower ear.

Sweet corn remains in the milk stage for a short time. The weather determines the length of this stage. Sweet corn remains in prime condition for only 1 or 2 days during hot (85°F and above) weather. As the sweet corn approaches maturity, check it frequently during typical summer weather to ensure high quality sweet corn.

Harvest sweet corn by grasping the ear at its base and then twisting downward. 

Storage

Use or refrigerate sweet corn immediately because its quality rapidly declines after harvest. If not refrigerated, standard sweet corn (su) varieties may lose 50% of their sugar content within 12 hours of harvest. Optimum storage conditions for sweet corn are a temperature of 32°F and a relative humidity of 95%. The maximum storage life for sweet corn is 4 to 8 days. Sugar-enhanced (se) and supersweet (sh2) varieties are slower to convert sugar to starch and may be harvested over a longer period. They also have a longer storage life.

Harvesting Baby Corn

Miniature ears of corn (baby corn) are popular items in restaurants and gourmet food stores. Although 'Bonus' and a few other varieties are grown specifically for their miniature ears, most baby corn is actually grown from regular sweet and field corn varieties. The ears are harvested when they are 2 to 4 inches in length and 1/3 to 2/3 inch in diameter at their base. Most sweet corn varieties reach this stage 1 to 3 days after the silks become visible.


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Photo credits: 1: SUPER FOX/AdobeStock; 2: SUPER FOX/AdobeStock; 3:CoreyOHara/AdobeStock; 4: Cindy Haynes; 5: Elena_Alex/AdobeStock 

Last reviewed:
June 2024