By Russell T. Nagata University of Hawaii at Manoa ADVERTISING College of Tropical Agriculture and Human Resources Komohana Research and Extension Center, Hilo Ask people what their favorite garden vegetable is and the answer for most is sweet corn. To
By Russell T. Nagata
University of Hawaii at Manoa
College of Tropical Agriculture and Human Resources
Komohana Research and Extension Center, Hilo
Ask people what their favorite garden vegetable is and the answer for most is sweet corn. To maximize its sweetness, it should be eaten as soon as possible after its harvested. And nothing beats sweet corn from the backyard garden. As I look back on all of my gardening adventures, growing and eating great fresh sweet corn either raw or cooked ranks high on the list of gardening accomplishments.
Sweet corn, Zea mays, like all corn, originated in South and Central America and is a purely domesticated crop. Explorations in wild areas have not resulted in finding patches of corn growing without the aid of humans. Sweet corn is differentiated from other corn by a genetic mutation that prevented or slowed down the conversion of sugars to starch. This mutation called “sugary” occurred in pre Columbian time in a Peruvian variety and was used by native populations as a kind of snack food. However, once the ear is harvested, the conversion of kernel sugars to starch is rapid, which leads to a rapid loss of sweetness.
For these “sugary” varieties the folklore was to have the water boiling prior to harvesting to insure the sweetest possible corn. In truth, sweetness is not lost that quickly, but shelf life for good sweet corn was a matter of days. A day on the counter will reduce sweetness, but sweetness would still be acceptable. Higher temperatures will accelerate the conversion of sugars to starch, so it is a good practice to refrigerate or ice harvested corn to preserve sweetness. In the 1950’s, discovery of a new gene for super sweetness was made in Illinois called shrunken 2 which greatly increased the sweetness of sweet corn. With this higher level of sweetness, a longer duration between harvest and consumption was made possible. Extension of shelf life for a week or more was now possible with proper postharvest handling. Over the years, other super sweet genes were discovered and used to create better sweet corn. The most widely used are the sugary extender and brittle genes. The brittle super sweet gene is favored by Dr. James Brewbaker, plant breeder who developed all of the University of Hawaii super sweet corn varieties. Nearly all mainland sweet corn varieties use the shrunken 2, sugary extender or a combination of both genes to confer sweetness.
Growing corn in Hawaii is a moderately easy task due to the tropical climate found throughout the Island. Site selection should be one that is easy to till and have water available for irrigation if needed. Your corn will need about 1 to 2 inches of rainfall each week for the first six weeks, after which water needs increase to 2 to 3 inches per week.
To grow a healthy corn crop, you will need about 2.5 pounds of triple-16 fertilizer or its equivalent from other fertilizer sources for every 100 square feet of garden. Additional nitrogen fertilizer, such as urea or ammonium sulfate should be applied as a side dressing when the plants have five to seven leaves, or about a month old. When setting up your corn plot, orient your rows or the long axis with the wind since it is a wind pollinated crop. It is best to plant corn in a block design, at least four rows wide, to improve pollination. Growth of sweet corn is highly dependent on day length and will grow taller in summer. During the winter months, sweet corn can be half the height of summer grown corn. In locations with gusty breezes, it is best to have a wind break to prevent your corn stalk from being blown over.
Sweet corn should be harvested when it reaches the peak of sweetness. In summer, this occurs approximately 18 days after the appearance of silk from the baby ears of corn. During the winter, cooler higher elevation locations, or with prolonged cloudy weather, maturity time will increase. At harvest maturity, the tips should feel well filled and the silks should be tan or brown in color. If you are still not sure if they are “ready,” peel back the husk from an ear or two and take a bite. The corn should be sweet and juicy.
Like you and I, many creatures love to enjoy your sweet corn. Major pest problems begin at planting where mice and birds snack on the newly planted seeds and emerging seedlings. Fungi and bacteria can be problematic in high rainfall areas. A number of insect pests can cause extensive damage to non-adapted sweet corn varieties. Many of the varieties developed by Dr. Brewbaker are highly tolerant of many diseases and insect pest found in Hawaii.
For more information on this and other gardening topics, please visit the CTAHR electronic publication website at http://www.ctahr.hawaii.edu/Site/Info.aspx or visit any of the local Cooperative Extension Service offices around the Island. I can be reached at russelln@hawaii.edu.
