How to Grow Corn in a Planter Box

Obtain a planter box at least 2 feet wide-by-3 feet long and a minimum of 2 feet deep. Make sure it least two holes in the bottom to allow good drainage.

Fill the bottom 3 to 4 inches of the planter with heavy rocks that weigh the box down to prevent it from becoming top-heavy and tipping when the corn stalks grow to their full height. Arrange the stones -- irregular-shaped rocks are best -- so that they don't block the drainage holes.

Fill the box in layers using 2 inches topsoil, 1 inch of peat moss and 1 inch of compost to make a rich, light-weight mixture that drains well. After each addition, blend the components by stirring lightly with a garden trowel.

Push 1-inch-deep holes into the soil with your finger or the handle-end of a trowel. Space the holes 4 inches apart. Avoid making any holes in a 4-inch margin around the planter box edge. Drop 1 corn seed into each hole, cover with soil and tamp down firmly. When the plants reach 6-inches high, thin the crop by pulling out enough stalks to leave an 8-inch spacing between the plants.

Water newly planted seeds and young seedling thoroughly, applying water whenever the top 1/2 inch of soil becomes dry. In the hottest days of summer, this could mean watering twice a day. Increase the volume of water as the plants grow. Allow the top inch of soil to dry before watering when the stalks reach 3 feet high or begin to tassel, but water until water drips from the drainage holes each time.

Spread a 1-inch layer of compost over the plant box surface, around the base of the corn stalks, six weeks after planting and again when the corn ears begin to develop. Alternately, apply commercial fertilizer formulated for vegetables, following the manufacturer's label instructions.

Clip two or three sections off each tassel when the silk on the corn ears reach 2 inches long. Brush the small, fuzzy pieces of pollen of the tassel sections onto the silk where it emerges from the corn. Repeat the process two or three times more, seven to 10 days apart. This technique facilitates pollination for corn growing in planter boxes where the bees and breezes that typically spread garden-grown-corn pollen are not as abundant.

Harvest corn when the ears are plump and the silk has turned brown. Stalks with multiple ears may yield fresh eating corn over a two- to three-week period.