The key to growing excellent sweet corn is growing healthy plants quickly, with adequate soil moisture, nitrogen and good pollination.
Corn should not be allowed to dry out during the growing season because it may stunt the plant, affecting the size and development of the ear. Plant corn in good Garden soil that has been given a boost with nitrogen fertilizer. Adding aged manure or compost to the soil is helpful.
Plant corn after May 10 in the Denver area or after the last average frost date in your area, because warm soils will help the seed get off to a good start. Plant corn in rows 30 inches apart. Plant two seeds in each hole, spacing the holes about a foot apart. Shorter, earlier corn varieties can be spaced closer together. Thin the corn to one plant in each hole. Corn is wind pollinated and should be planted in blocks rather than long, single rows.
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. Harvest corn about three weeks after the silk emerges, or when kernels are well filled and pressure from your fingernail produces a milky liquid. To remove the ear, grasp it firmly, bend it toward the ground and pull with a twisting motion. Cook, freeze or eat corn immediately after harvest for the best sweet corn on the block.
For more information, see the following Colorado State Extension fact sheet(s). http://www.ext.colostate.edu/ptlk/1816.html