Some seeds need light in order to germinate, but many do not. Seed packages will usually indicate what your particular selection requires. It is important to follow the directions given on the package for planting depth. In addition to light requirements, seeds that are planted too deep will not have enough stored energy to reach the soil surface and may die in the process. After germination occurs, seedlings require about 12 to 16 hours of light a day.
Intense light is necessary to prevent spindly or leggy seedlings.
If you are growing under lights, make sure the light source is 4 to 6 inches above the plants. In a sunny window, turn the seedlings regularly to avoid leaning. This will help to produce stockier transplants provided enough light is available. Before planting in the garden, gradually acclimate transplants to the outdoors. Start by putting them outside on cloudy days or in a shaded location then after a few days work them into more light and exposure.