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Getting the Sweet Corn for Utah Gardens

Getting the Sweet Corn for Utah Gardens

Estimated read time: 7-8 minutes

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Sweet corn is a popular vegetable in Utah. It grows best with full sun and fertile, well-drained soil. Add organic matter and a complete fertilizer to the soil before planting. Plant the seeds when soil temperatures reach 60ºF.

Space rows 24-30 inches apart, plant seeds 1-2 inches deep and space seeds 9-12 inches apart in the row. Plant corn blocks at least four rows wide to ensure good pollination. Transplant or direct seed sweet corn under clear plastic for early production. Plant sweet corn every 10-14 days for a continuous crop throughout the season.

Sidedress sweet corn with nitrogen fertilizer when plants have 8-10 leaves. Sidedress again when silks appear.

Corn requires regular watering, so maintain soils near field capacity. Water stress reduces yield and ear quality. Organic mulches help conserve water, add nutrients and reduce weed growth

Harvest the corn when ears are plump, silks are dry and kernels are milky. Use ears immediately for best quality.

Recommended cultivars There are many different sweet corn cultivars for the home garden. The major differences include maturity dates and sugar content. Sweet corn maturity ranges from 60 to 90 days depending on cultivars.

Early cultivars have smaller ears, are not as sweet and those that mature later. Early cultivars do well with short growing seasons and cool temperatures. Late maturing cultivars adapt better to long seasons and warm temperatures.

Sugar content in the kernels is also important. Sweet corn cultivar are classified as • Standard sugary (su) • Sugary enhanced (se) • Super sweet (sh2)

Which cultivars are best to plant? • Standard types germinate better in cool soils than the se or sh2 types. All types germinate well in warm soils. Eating quality is adversely affected if su, se and sh2 mature together

If cross pollination occurs, the extra sweetness of the se and sh2 types is lost. The corn then tastes more like the standard cultivars.

Time plantings so they tassel at different times. Most sweet corn cultivars will grow in Utah, but not all are available. Most garden centers and nurseries carry cultivars that grow well and produce high quality, flavorful ears.

Here is a partial list of cultivar proven to grow well in Utah • Corn Type Selected Cultivars Comments • Standard (su) Sweet Corn • Earlivee, Jubilee, Silver Queen, NK199 • Lower sugar content than se or sh2 types • Good cool soil germination

• Sugar Enhanced (se) Sweet Corn • Incredible, Sugar Buns, Miracle, Peaches and Cream • Higher sugar content, maintains quality long after harvest • Better cool germination than sh2 types

• Super Sweet (sh2) Sweet Corn • Honey & Pearl, Phenomenal, How Sweet It Is, Supersweet Jubilee • Poor germination in cool soils • Extra sweet flavor • Isolation needed from su and se types • Maintains quality after harvest

How to Grow Soil Preparation: Before planting, incorporate 2-4 inches of well composted organic matter. Add1-2 lbs. of (16-16-8) fertilizer per 100 square feet of planting area. Work the compost and fertilizer into the top 6 inches of soil.

Sweet corn is a warm weather vegetable. It requires soil and air temperatures above 60ºF for best germination and plant growth. Plant after the last frost-free date for your area. For earlier production plant transplants after the frost-free date. Sow seeds 3-4 weeks earlier if planted through or under clear plastic tunnels.

It takes 3-4 ounces of seed to plant 100 feet of row. Plant in blocks of 4 or more rows to improve pollination and production. For high-density corn, plant seeds on 15 by 15 inch squares.

For continuous production plant every 10-14 days until mid-July. Corn requires 60-90 days to mature depending on cultivar. Continuous production is possible by planting a 65, 70, 75, and 80 day cultivar of the same type (su, se, or sh2) all at the same time. This ensures production over a longer time period. With planning sweet corn can be produced for two to three months.

Sweet corn requires regular watering throughout growth for best production. Maintain soils near field capacity. Water needs are critical during tasseling, silking and ear formation. Drought stress during ear development decreases yield, lowers kernel quality and affects flavor. Watering needs depend on soil type.

Fertilization: In addition to the preplant fertilizer sweet corn needs additional nitrogen fertilizer to produce optimum yields. Sidedress sweet corn with 1/2 lb. of 34-0-0 per 100 square feet when plants have 8-10 leaves. Add an additional 1/4 lb. when the first silks appear. Place the fertilizer 6 inches to the side of the plant and irrigate it into the soil

Mulches and Row Covers: Clear plastic mulches help conserve water, provide some frost protection and allow earlier planting and maturity. It stimulates weed growth under the plastic.

Fabric row covers protect young plants from frosts

Organic mulches help control weeds but reduce soil temperatures. These include grass clippings, straw and shredded newspaper. Sumer mulching reduces water loss and improves nutrient availability.

Problems Weeds: Control weeds with regular cultivation especially when plants are small. Once sweet corn gets large, it will out-compete the weeds. Cultivate carefully to avoid root damage which slows plant growth.

Insects and Diseases: Aphids are green or black soft-bodied insects. They feed on leaves, tassels and ears. Plants become crinkled, curled and growth is stunted when plants are small. Honeydew makes plants and ears sticky and aphids cause cosmetic damage to the ears.

To control aphids, use insecticidal soaps, appropriate insecticides and wash off the insects with a strong stream of water.

Corn earworms larvae feed on silks and ears of corn. They damage symptoms include holes in ear tips, loss of silks, and damp excrement near silk. Spray with BT or appropriate insecticides. Regular applications are necessary to protect the plants. Also, apply mineral oil to silks or remove damaged part of ear at harvest.

Cutworms or army worm larvae feed near the soil surface and sever the plants close to the ground. Most damage done at night. Use barriers or collars around plants. Keep organic mulches way from young plants.

Root rots and damping off cause seedlings to darken, wilt and die. They are usually a problems during cool, wet spring conditions. Use treated seed and allow soils to dry before re-watering

Smut causes white fungal galls that form on the tassel, stem or ear. Early plant infection will stunt growth and deform ears. Remove and destroy galls and severely infected plants. Plant resistant cultivars.

Wilt Diseases cause wilting leaves, streaking and drying of leaves, stalk rotting, and plant lodging and plants often die. Remove infected plants and maintain clean garden practices.

Harvest and Storage: Corn matures 15-24 days from silk emergence, depending on temperature. Ears are mature when silks are dry and brown. The husks should appear moist and green and kernels in the tip of the ear should be plump and release milky juice when punctured. Ears can be harvested over a 5-7 day period.

For best quality and flavor, harvest and use immediately. To harvest, grasp the ear, snap downward while twisting the ear. Sweet corn can be stored for several days if refrigerated. Do not husk until ready for use.

Productivity: Expect one ear per plant. Plant 10-15 feet of row per person for fresh use. Plant 30-40 feet of row per person for canning or freezing. Expect about 10 dozen ears per 100 feet of row.

Nutrition: Sweet corn is high in fiber, potassium, folic acid, and vitamin A. One ear contains 80 calories and 20 grams of carbohydrates.

Common Problems: When I plant corn early in season it does not come up well. How can I get a better stand? It is best not to plant too early in the spring. Wait until the soil is warm, preferably above 60ºF. Try sowing more seed and thin to the correct distance after they emerge. Fungicide seed treatments may also be helpful.

For early plantings, sow su types or plant through clear plastic. The sh2 cultivars do not germinate well in cold, wet soil. For early plantings, sow su types or plant through clear plastic.

Poor kernel development at the tip is often caused by • 1) hot, dry weather during silking and pollination • 2) planting seeds too close together • 3) low soil fertility • 4) poor natural pollination

Extra shoot growth or suckering is common in sweet corn if plants are grown far apart in the rows. Most suckers do not produce usable ears. Removal does not increase plant productivity. Plant the seeds closer together to decrease sucker formation and increase ear yield.

Raccoons and skunks severely damage sweet corn. If you grow large amounts of corn, an electric fence helps. Have the fence operating before the corn is ripe.

Sweet Corn Reproduction - Male flowers are tassels which are covered with spikelets. These hold the anthers which produce the pollen. - Female flowers are silks. Each potential kernel produces a silk and the pollen grain lands on that and grows down the silk and fertilizes the kernel.

(article based on Dr. Dan Drost's Fact Sheet)

Written by: Larry A. Sagers Extension Horticulture Specialist Utah State University

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Larry A. Sagers


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