Midwest Vegetable Guide - 2022 - 269

Sweet Corn - Horticulture
Planting and Spacing
Sweet Corn - Horticulture
Major update by Ben Phillips, Liz Maynard, Bill Tracy - Oct
2020
Reviewed by Liz Maynard - Aug 2021
Crop Description
Sweet corn (Zea mays subsp. mays) originates from a wild
relative in Central America. Sweet corn is usually described
by color (yellow, bicolor, or white) and by the major gene
names that make it sweet. Despite the many marketing terms
and trademarked names, sweet corn can be categorized into
five major types.
The original sweet corn (called standard, sugary, or su)
contains the su1 genetic variant that makes it sweet instead of
starchy like field corn. Sugary sweet corn is grown today
primarily for processing and specialized markets.
A second type of sweet corn (called sugar-enhanced, sugary
enhancer, EH, or se) contains the se1 genetic variant that
increases sugar content and makes the kernels more tender.
Heterozygous se corn has one copy of the se1 mutation and
homozygous se corn has two copies of the se1 mutation,
increasing its effect. Sugar-enhanced sweet corn is grown
primarily for direct retail sales and local wholesale markets.
A third type of sweet corn (called supersweet, ultrasweet,
extra sweet, or shrunken-2) contains the sh2 genetic variation.
This type typically has a higher sugar content than su corn,
and the sugar content does not decline rapidly after picking,
so it remains sweet for several days after harvest. Kernels
typically are not as tender as se corn. Shrunken-2 (sh2) types
are grown for retail sales, local fresh markets, and wholesale
shipping markets.
Many of the newest sweet corn varieties combine the sh2 (or
similar genes) with se and/or su genetics. Sugar-enhanced
sweet corn that also includes sh2 (or similar) genes is called
synergistic, and may be abbreviated as sesh2, syn, or sy corn.
Current synergistic varieties are typically very sweet and very
tender. Shrunken-2 sweet corn varieties with genetics
increasing tenderness and flavor are categorized as
augmented or improved supersweet or sh2, sometimes
abbreviated shA. These varieties are typically extremely
sweet and tender. Many of these varieties have performed
well in midwestern trials and receive top ratings for eating
quality. The new types are often identified by trademarked
brand names.
Sweet corn varieties with resistance to certain insects, and/or
glyphosate or glufosinate herbicides are also available.
Common spacing is 30 to 40 inches apart between rows.
Plant early varieties 8 to 10 inches apart in the row, late
varieties 9 to 12 inches apart in the row. Seed 10 to 15
pounds per acre.
Sweet corn flavor is affected by pollen source. Isolate all
sweet corns from all other non-sweet corns, including dent
(field), flint (Indian), flour, and popcorn by 250 feet or by a
14-day difference in tasseling dates. Likewise, supersweet
(sh2) and augmented (shA) sweet corn varieties must be
isolated from sugary (su), sugar-enhanced (se) and synergistic
(syn) types. If not isolated, kernels of both varieties will be
starchy instead of sweet. Refer to the table below for isolation
requirements or check with your seed supplier.
To maintain color purity, isolate white corn from yellow or
bi-color corn. Pollen from yellow or bi-color corn will cause
some yellow kernels in white varieties. Pollen from yellow
corn will lead to extra yellow kernels in bi-color varieties.
Pollen from white corn will not affect the color of yellow or
bi-color varieties.
Table of Sweet Corn Isolation Requirements
Type
Sugary (su)
Sugar-enhanced (se)
Synergistic (se x sh2 = syn)
Shrunken-2 (sh2)
Augmented (su x sh2 = shA)
Isolate from
sh2, shA
sh2, shA
sh2, shA
su, se, syn
su, se, syn
Fertilizing
pH: Maintain the soil pH between 6.0 and 6.5.
Before planting, apply 40 to 60 pounds N per acre, 0 to 100
pounds P2O5 per acre, and 0 to 150 pounds K2O per acre
based on soil test results and recommendations from your
state. For early plantings, apply a starter fertilizer at planting
2 inches below and 2 inches to the side of the seed, but do not
exceed 80 to 100 pounds of N plus K2O per acre. On irrigated
sandy soils reduce N to 10 to 20 pounds per acre and apply in
a band of starter fertilizer. On sandy soils, broadcast 30
pounds or band 15 pounds of sulfur per acre.
Sidedress with 30 to 60 pounds N per acre when plants are 5
to 10 inches tall. On irrigated sandy soils, apply two
sidedressings of approximately 40 pounds N per acre each:
one when 4 to 5 inches tall (4th to 5th leaf), and the other at 10
inches tall (10th to 12th leaf).
Reduce the amount of fertilizer N applied by the value of N
credits from green manures, legume crops grown in the
previous year, compost and animal manures, and soils with
more than 3 percent organic matter. The total amount of N
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Midwest Vegetable Guide - 2022

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