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Sweet Corn Seed Starting Tips

Seedling Corn
Start corn seeds
Corn seedling

Corn is a tender, warm-weather crop. Sweet corn is commonly grown in gardens.

  • Sow corn in the garden 1 week after the last frost when the soil temperature has warmed to at least 65°F (18°C).
  • Start corn indoors 4 weeks before transplanting it to the garden. Seedlings as small as 1 inch (2.5 cm) can withstand transplanting.
  • Succession plant corn 1 to 2 weeks apart to extend the harvest. Time the last sowing so that harvest comes a week or two before the first expected frost in fall.
  • Planting corn in cold soil or chilly weather risks poor stands and poor yield.
  • Corn matures 60 to 100 frost-free days after sowing.

Corn Sowing and Planting Tips

  • Grow corn from seeds or seedlings.
  • Corn seed is viable for 2 years.
  • Direct sow corn in the garden in spring after all danger of frost has passed and the soil has warmed to 60°F (16°C).
  • The optimal soil temperature for growing corn is 65°F to 75°F (18-24°C). Corn will not germinate in soil chillier than 50°F (10°C).
  • To start plants indoors, sow seed in peat pots 4 to 3 weeks before planting out. The optimal indoor temperature should be 70°F (21°C) until germination.
  • Sow seed 1 inch (2.5 cm) deep.
  • Seeds germinate in 4 to 10 days.
  • Transplant corn into the garden after the soil has warmed to at least 70°F (21°C).
  • Space corn 12 inches (30 cm) apart in all directions; plant corn in blocks of at least 4 rows for optimal pollination. About 4 plants for each square foot.
  • Keep the soil just moist; letting the soil dry out will interrupt pod development.
  • Fertilize with fish emulsion or a soluble complete fertilizer at half strength.
  • Add aged compost to planting beds in advance of transplanting.
  • Corn prefers a soil pH range of 6.0 to 7.0.
  • Grow corn in full sun for best yield.
  • Common corn pest enemies include aphids, armyworms, corn earworms, corn maggots, corn rootworms, cucumber beetles, flea beetles, Japanese beetles, leafhoppers, seed corn maggots, birds, and raccoons.
  • Common diseases include bacterial blight, mosaic virus, rust, corn smut, southern corn leaf blight, and Stewart’s wilt.

Interplanting: Plant corn with bush beans, beets, cabbage, cantaloupe, cucumbers, melon, potatoes, pumpkins, and squash.

Container Growing Corn: Corn may not be a good choice for containers unless you have large containers that can hold multiple plants (to insure pollination). Choose a container 21 inches (53 cm) wide and 8 inches (20 cm) deep; plant at least 3 plants per container.

Corn Planting Calendar

  • 4-3 weeks before transplanting seedlings to the garden: start seeds indoors.
  • 1 week before the last frost in spring: direct sow seed in the garden; protect seedlings from the chill with a row cover; minimum soil temperature should be 50°
  • 2-3 weeks after the last frost in spring sow directly in the garden without protection.
  • Every 2 weeks sow succession crops for a continuous harvest.
Corn seedlings seed start corn
Sow corn in the garden 1 week after the last frost when the soil temperature has warmed to at least 65°F (18°C). Start corn indoors 4 weeks before transplanting it to the garden.
  • Early planting sweet corn varieties include ‘Early Sunglow’ and ‘Polar Vee’; midseason varieties include ‘Golden Bantam’ and ‘Honey and Cream’.
  • Late-season varieties include ‘Country Gentleman’ and ‘Silver Queen’.
  • For small gardens try ‘Golden Midget’ and ‘Tom Thumb’.

Botanical Name: Zea mays var. rugosa

Corn is a member of the Poaceae or grass family.

More tips: How to Grow Corn.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

Comments

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  1. Squirrels are even more of a threat to your corn than raccoons, since squirrels are more numerous. Set conibear 110’s out in ground-sets when you plant. If you wait until the corn ripens, it will be too late. You’ll never kill all of them.

  2. I have corn that is tasseling very quickly but no ears. Growing extra tender corn seeds and sugar buns. In containers. Lots of greenery. It’s about 2 feet up from buckets in height now. Not many silks. Any suggestions?

    • Early or pre-mature corn tasseling is often caused by stress–planting too early, weather too warm or too cold, or not enough moisture. Usually the plant will continue to grow and ears will form as the season goes on. If you want to hedge your bet, plant a second crop of corn now; choose a variety that can mature a few weeks before the first expected fall frost.

  3. i have several corn plants that are trying to start new stocks off the sides off them. do i trim them off so plant stays strong?

    • The new shoots forming on the side of your corn stalks are commonly called “tillers”–or you can call them suckers. Suckering or tillers is a sign that the plant is growing healthy and happy. Sometimes tillers produce extra ears of corn, but often they do not. And they do no harm to the plant. Be careful if you prune them off that you do not damage the main stalk or leave a wound through which pests or disease can enter the plant. That said, probably a good course of action is to let them be.

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