Southeastern U.S. Vegetable Crop Handbook - 2022 - 119

There are three primary genes contributing to sweetness in
sweet corn. They are; normal sugary (su), sugary enhanced (se),
and supersweet or shrunken-2 (sh2
).
Normal sugary sweet corn (su) has been enjoyed for many
years. Su sweet corn is known for its creamy texture and mild sugars;
however, sugars in these cultivars are rapidly converted into
starch if not cooked the day of harvest. These cultivars are commonly
sold in farmer's markets and roadside stands.
The sugary enhanced (se) sweet corn gene, known under
trade names such as Everlasting Heritage have varying degrees
of increased sugar content with a creamier kernel texture as
compared to su sweet corn types. This translates into increased
sweetness with a smoother kernel texture. Another advantage is
that se sweet corn types maintain their quality for a longer period
of time than normal sugary sweet corn types (su).
Cultivars of " Supersweet " or " shrunken " sweet corn (sh2
)
derive their name from the appearance of the dried kernel which
is much smaller than kernels of su or se sweet corn types. Recently
germination of sh2
sweet corn cultivars has been improved
and is now comparable with the su and se types. Seed
of supersweet (sh2
) sweet corn cultivars should be handled very
gently and the use of plateless planter is recommended to prevent
damage to seed. Many older supersweet cultivars require
warm soil (70°F or higher) to germinate since they are less vigorous
than the se or su genotypes. Supersweet sweet corn (sh2
)
cultivars have a crunchier kernel, are sweeter than su and se cultivars,
and will delay the conversion of sugar to starch extending
their shelf life.
Xtra-tender, Ultrasweet, and Triplesweet are names for the
latest development in sweet corn cultivars. These new types of
sweet corn combine the genetics of sh2
, se, and su genotypes.
These cultivars are high in sugar levels, hold well in storage, and
have a pericarp which is tender (this improves the eating quality
of the sweet corn). Plant these cultivars using the same recommendations
as those of the sh2
types of sweet corn.
Isolation requirements for the sweet corn genotype are important
in order to obtain the highest quality sweet corn. Supersweet
(sh2
) sweet corn must be isolated by a distance of 300 feet or 12
days difference in silking date to avoid cross pollination from
field corn, pop corn, normal sugary (su), and/or sugar enhanced
(se) types. Failure to properly isolate the sh2
genotype will result
in it producing starchy, tough kernels. Isolation of sugary
enhanced from normal sugary sweet corn types is recommended
to maximize quality; however, quality is usually very minimally
affected should cross pollination occur. It is recommended
that augmented sweet corn types be isolated from all other sweet
corn types for best quality.
Another important development in sweet corn cultivar development
is the incorporation of the BT gene (called BT sweet
corn). BT sweet corn has been genetically modified by incorporating
a small amount of genetic material from another organism
through modern molecular techniques. In sweet corn, the incorporated
BT genes is particularly effective in providing protection
against European corn borer and corn earworm. The protein
produced by the BT gene is very selective, generally not harming
insects in other orders (such as beetles, flies, bees, or wasps)
2022 Vegetable Crop Handbook for Southeastern United States
but more importantly this protein is safe for consumption by
humans, other mammals, fish, and birds. Syngenta Seeds has incorporated
the BT gene into several sweet corn cultivars that are
sold commercially under the trade name of Attribute followed by
a series of numerals to identify the cultivar. Certain restrictions
such as isolation, minimum acreage requirements, and destruction
of the crop are part of the terms of contract when purchasing
BT sweet corn seed.
In general, when selecting a cultivar, be sure to evaluate its
acceptance in the market. Plant small acreages of new cultivars
to test market their acceptance.
Seed Treatment. Check with seed supplier to ensure seed was
treated with an insecticide and fungicide. Information on seed
treatments can be found under SEED TREATMENTS in the disease
management section of the handbook.
Seeding and Spacing. Seed is sown as early as February in
more southern regions on light, sandy soils. Use a high vigor
seed variety for early plantings. Seed is drilled in the field about
1 inch deep. Varieties are spaced 30 to 42 inches apart between
rows depending on cultural practices, equipment, and seed size.
In-row spacings range from 6 to 12 inches apart, with smalleared,
early seasons varieties planted closest.
SWEET CORN PLANTING DATES
Spring
AL North
AL South
GA North
GA South
KY East
KY Central
KY West
LA North
LA South
MS North
MS South
NC East
NC West
OK
SC East
SC West
TN East
TN West
VA East (coastal)
VA West (mountain)
NR = Not recommended
Mulching. The use of clear plastic mulch will improve stands,
conserve moisture, and produce earlier maturity. Corn is seeded
in the usual manner, except 10 to 20 days earlier in double rows
14 inches apart and on 5- to 6-foot centers. Apply herbicide
and then cover with clear, 4-foot-wide plastic. Allow plastic to
remain over plants for 30 days after emergence, then cut and remove
plastic from field. Plants can then be cultured in the usual
manner. A nematode assay is recommended before using this
system. If nematodes are present in the soil, control measures
are necessary before planting. Use a high vigor seed variety to
avoid uneven and reduced stand.
119
4/15-5/30
2/1-4/30
4/15-4/30
2/1-3/31
5/1-6/15
4/20-7/10
4/10-7/20
3/1-5/15
2/15-5/1
3/20-4/9
2/21-3/14
3/15-4/30
4/15-6/15
3/25-4/30
3/1-4/15
3/30-5/30
4/15-6/30
4/15-6/15
3/20-8/10
3/30-7/30
Fall
NR
7/15-8/15
NR
7/15-8/15
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
Southeastern U.S. Vegetable Crop Handbook - 2022

Table of Contents for the Digital Edition of Southeastern U.S. Vegetable Crop Handbook - 2022
