Growing Sweet Corn - April 27, 2016
Jeff Schalau, Agent, Agriculture & Natural Resources
University of Arizona Cooperative Extension, Yavapai County


Sweet corn is a summertime treat. In the garden, it requires a large space, ample water, and close attention to nitrogen fertility. If you grow vegetables and have some space, you should grow sweet corn at some point to experience it. This edition should get you prepared to have a successful crop of summer sweet corn.

There are many sweet corn varieties to choose from. The main differences are in maturity dates and sugar content. Sweet corn has a maturity range of 60 to 90 days depending on variety. Early varieties do well where the growing season is short and temperatures are cool, but are smaller and less sweet. Late maturing varieties are better adapted to long seasons, warm temperatures, and should do well in the Verde Valley.

Sweet corn varieties are classified as standard sugary (su), sugary enhanced (se), or super sweet (sh2). Standard (su) types germinate better than the se or sh2 types in cool soils. All types germinate well in warm soils. Eating quality may be adversely affected when su, se and sh2 are planted together and tassel at the same time. If cross pollination occurs, the extra sweetness of the se and sh2 types is lost and they taste like the standard variety. It is probably best to stick with one variety or, at the least, grow all the same types (all su, all se, or all sh2).

Corn requires 60-90 days to mature depending on variety. Utah State University offers the following suggestions for sweet corn varieties: for su types, consider Earlivee, Jubilee, Silver Queen, or NK199; for se types, consider Incredible, Sugar Buns, Miracle, or Peaches and Cream; and for sh2 types, consider Honey & Pearl, Phenomenal, How Sweet It Is, or Supersweet Jubilee. You can also talk to your corn-growing neighbors about their favorite varieties.

Your sweet corn should be planted where is has full sun and well-drained soil. As with all vegetable crops, amend the soil with compost and a complete fertilizer (aged manures can also be used) prior to planting. Corn must be planted in a large block, not long single rows, to ensure good pollination and ear development. Three to four ounces of sweet corn seed is needed per 100 feet of row. Within the block, plant corn seed by direct sowing when soils are above 60F. Rows should be spaced 24-30 inches apart and seeds planted 1-2 inches deep and 9-12 inches apart in the row. If you have the space, successive plantings every 10-14 days until early July will provide you with sweet corn over an extended period in summer.

Sweet corn requires regular watering throughout the growth cycle for best production. Do not allow the soil to dry down significantly at any time in the season. Water needs are especially critical during tasseling, silking, and ear formation. Watering amounts and frequency depend on soil type with sandy areas needing more frequent applications and clayey areas requiring less frequent applications.

As stated above, nitrogen is an important nutrient for corn which is, in reality, a large annual grass plant. In addition to the fertilizer used when preparing the soil, sweet corn needs nitrogen fertilizer during the growing season for optimum yields. Sidedress sweet corn with 1/2 lb of 46-0-0 (urea) or 2 lbs of 10-10-10 per 100 square feet when plants have 8-10 leaves on them. Sidedressing is simply applying the fertilizer 6 inches to the side of the row next to the plant. This is followed by a second sidedressed application of half as much nitrogen as was applied during the previous fertilization when the first silks appear. Sidedressed fertilizer should be watered in following applications.

Reducing weed competition during the growing season will improve corn production. Mulching will reduce weed growth and decrease evaporation from the soil surface. If weeds are to be hoed, use extra care near the root systems of the developing corn crop.

The main insect pests of corn are corn earworms, cutworms, and sometimes, aphids. Corn earworm caterpillars must be managed with either Bt or other appropriate insecticides. Cutworms can be controlled by using small protective collars (I use 12 ox paper cups with the bottom cut out) around the developing seedlings. Aphids can be managed using insecticidal soaps, appropriate insecticides, or strong water stream to dislodge the insects. See links below for additional information.

Follow the Backyard Gardener on Twitter use the link on the BYG website. If you have other gardening questions, call the Master Gardener help line in the Camp Verde office at 928-554-8992 or e-mail us at verdevalleymg@gmail.com and be sure to include your name, address and phone number. Find past Backyard Gardener columns or provide feedback at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.

YouTube Video: How to Plant Corn (Extension Agent, Ron Patterson, Utah State University).

Additional Resources

Sweet Corn in the Garden
Utah State University Extension

extension.usu.edu/files/publications/publication/HG_Garden_2005-10.pdf

Sweet Corn
University of Illinois Extension

cru.cahe.wsu.edu/CEPublications/pnw0170/pnw0170.pdf

Growing Sweet Corn in Home Gardens
University of Tennessee Agricultural Extension Service

extension.tennessee.edu/publications/Documents/SP291-E.pdf

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Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr. #C
Prescott, AZ 86305
(928) 445-6590
Last Updated: April 18, 2016
Content Questions/Comments: jschalau@ag.arizona.edu
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