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Science-based gardening information for Colorado communities from CSU Extension, Denver Botanic Gardens, and Green Industries of Colorado.

1816 – Sweet Corn   arrow

The key to growing excellent sweet corn is providing rich amended soil, ample moisture and fertilizer and growing it in block-rows for good pollination.

Sweet corn on the stalk

When should I plant corn?

Plant corn after the danger of frost is over, usually May 10 in the Denver area. This date may be later (or earlier) in other parts of the state. Warm soils will help the seed get off to a good start. Soil temperatures 50 ̊ F or up to 60 ̊ F for super sweet corn types (measured two inches deep) ensure good seed germination. Garden soil which has been amended with aged manure or compost (if needed) and given nitrogen fertilizer help give plants a good start.

What is the best method of planting corn?

Plant two corn seeds in each hole, spacing the holes about 12-15 inches apart. Plant in rows 30-36 inches apart, planting several rows together forming a block of rows. Corn is wind pollinated and should be planted in blocks rather than long, single rows for best pollination. Shorter, earlier corn varieties can be spaced closer together. Thin the corn to one plant from each hole.

Is watering corn very important?

Since adequate soil moisture is crucial for plants to form tassels, silks and ears, soil around corn should not be allowed to become too dry during the growing season. Uneven watering may stunt the plant, affecting the size and development of the ear.

When should I fertilize corn?

Fertilize corn around the first week of July and keep weeds under control. Two ears usually develop on a corn plant, but the largest one grows closer to the top.

When should I harvest corn?

Harvest corn after the silk is dried and brown and the husk is still green or when kernels are well filled and pressure from your fingernail produces a milky liquid. Raccoons will also know when corn is ripe, so be vigilant as corn matures, so you don’t lose your crop. Pick in the early morning for best flavor.

How do I remove the ear of corn?

To remove the ear, grasp it firmly, bend it toward the ground and pull with a twisting motion. Cool ears after picking, freeze or cook and eat corn immediately after harvest for the best tasting sweet corn.

For more information, see the following Colorado State University Extension fact sheet(s).

For more information, see the following Planttalk Colorado™ script(s).

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