Growing Sweet Corn for the Whole Summer


| 7/3/2014 9:18:00 AM


Tags: sweet corn, corn, Virginia, Pam Dawling,

corn fieldStart planting sweet corn early. When to plant sweet corn? Rowcover can be used to pre-warm soils (and then keep cold temperatures and birds off the germinating seeds). Clear plastic mulch can increase soil temperature and germination rate, and conserve moisture, producing earlier harvests. Spread the plastic over the seeded beds and slit it when the seedlings emerge. Cut and remove it thirty days after emergence. Weed-free seedbeds are needed for this method to work organically, and plastics disposal is an issue.

Transplanting Sweet Corn

Direct sowing is the usual way of planting sweet corn, but transplanting can also be successful. It is important to transplant before the plant gets too big and the taproot takes off. 2-3” (5–7.5-cm) plants seem OK. Corn has no tolerance to frost. Escape from a late spring frost is possible if the seedlings are less than two weeks old and not yet very tall, as the growing point may still be underground. Thus, in a spring that promises to be warm and dry, you can risk an early planting as much as 2–3 weeks before the last frost date. Having some transplant plugs for a backup helps reduce the risk level. We usually prepare some plugs the same day we sow our first corn outdoors and use these to fill gaps at the first cultivation. We use 200-cell Styrofoam Speedling flats (1", 2.5 cm cells). We float these in a tank of water until we set them out. Some vegetable seedlings would drown if continuously in water, but corn does not. The plugs transplant easily using butter knives.

But don’t plant corn too early! Sweet corn needs warm soil. 50°F (10°C) is the absolute minimum, and applies to treated seed and OP or (su) varieties only. 60°F (15.5°C) is better for most, and 65°F (18°C) or higher is required by some varieties. Common phenology signs for the season being advanced enough to sow corn are that oak leaves are the size of squirrels’ ears and that ragweed is germinating. For us the first corn sowing date is usually around April 26, which is also our average last frost date. Either pre-warm the soil, use transplants, or wait for warm soil.

sweet corn

Avoid mixing types of corn. There’s a confusing aspect of hybrid corn varieties: There are several genotypes, and if you inadvertently plant a mixture of different types, it can lead to starchy unpleasant-flavored corn. Also don’t plant Indian corn, popcorn or any kind of flint or dent corn within 600′ (180 m) of your sweet corn. For this reason we grow only sweet corn in our garden. Ignore those cryptic catalog notes at your peril!

Normal sugary (su or ns) types have old-fashioned corn flavor but are sweeter than open pollinated varieties, although the sweetness disappears fairly rapidly after harvest. Not a problem for home gardeners who can cook the corn they harvested earlier that day. Most can germinate well in cool soil. Sugary-enhanced (se) and sugary enhanced homozygous (se+ or se-se) types are more tender, and usually sweeter, than (su), and slower to become starchy after harvest. Triplesweet sugary enhanced (se-se-se) were created to be sweeter than se-se. We grow these first three types, and avoid the newer types below – sweet and simple!




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