How to Grow Radishes Underneath a Grow Light

Fill the planting container to the top with the soil-less growing medium. Spray the medium with water to make it damp.

Scatter the radish seeds evenly over the top of the growing medium. Sprinkle about 1/8-inch of medium over the tops of the seeds.

Place the container in a location with a temperature between 40 and 70 degrees Fahrenheit. An unheated garage, porch or basement would be ideal.

Position the fluorescent grow light about 6 inches over the planting container. Using fluorescent bulbs will ensure that the light you provide for the radishes does not provide heat -- cool light is necessary or you risk warming the radishes too much as they grow.

Provide about six hours of light out of each 24-hour period. Keep the growing medium evenly moist by spraying it with water when it begins to dry.

Raise the grow light as the radishes begin germinating. Keep the grow light about 6 inches above the seedlings at all times.

Thin the radish seedlings by pulling the weakest seedlings when they are about 3 inches high. Leave the strongest seedlings growing about 4 inches apart in the container.

Harvest the radishes when they become about 1 inch in diameter. Grasp the radishes by the stems and pull them carefully from the containers.