Seedlings grow dark green and sturdy in any cool indoor spot under artificial light. Many types of fixtures are available for growing plants indoors. Buy one of the many commercial fixtures available (search on line for “light gardens”), or make your own.
Because incandescent bulbs give off too much heat for the amount of light produced, fluorescent bulbs are usually used. Although some plants need balanced spectrums for blooming, the least expensive cool-white or warm-white fluorescent bulbs grow healthy seedlings. Fluorescent bulbs sold as “grow lamps” cost more, and aren’t necessary for seedlings. Because fluorescent bulbs are most efficient their first year, with their intensity diminishing as time passes, replace the bulbs every couple of years, or when the ends begin to darken.
A simple light source is a pair of 4-foot cool-white fluorescent bulbs in a hanging utility fixture. Hang the fixture on chains above a table or shop bench in a way that makes it easy to raise and lower the light.
Fluorescent bulbs give off a fair amount of heat. You can use them as a heat source for germination by hanging the lamps just over the soil surface. If they are in a cool room, boost the heat with a heating cable or a 75-watt incadescent lamp under the table to give bottom heat.
For the first couple of weeks after the seedlings germinate, set the lights about 3 inches above the seedlings. The lights can be left on 24 hours a day at this stage. As the seedlings grow, raise the light to 4 to 6 inches overhead and reduce the exposure to 14 to 16 hours a day. Use a simple lamp timer to turn the lights on and off.