Flourescents

• A simple grow light can be constructed with two standard 4 foot fluorescent light fixtures. Cut a sheet of plywood just larger than the two fixtures side by side. Drill holes in the backs of the fixtures and screw them to the plywood sheet side by side. Turn them over and attach four screw-in hooks to the corners of the plywood. Attach chains from corner to corner to make two loops at either end. Screw a couple of hooks to the ceiling above the seedling trays and you can hang the lights at whatever height you need. Wire the fixtures to a ceiling electric junction or attach an extension cord long enough to reach the nearest plug-in. Standard fluorescent bulbs will provide adequate growing light if you run them 24 hours a day. If you use full spectrum bulbs, follow the manufacturer's suggestions for how long to expose your plants. If you place the lights too close or expose the plants too long you can sunburn them.
  
  

LEDs

• LED light fixtures can be attached to the same plywood back and hung by chains from the ceiling as described above. Ninety watts of LED light fixtures produce the same growing spectrum range of light as a 400-watt metal halide or HPS "grow light". The diodes last more than 100,000 hours and can use less than a third of the power of other light sources.
  
  

Usable Light

• To make the light more even and help the plants grow evenly, you'll need to surround your growing area with white surfaces. Masonite or thin plywood or white painted walls help bounce the light around and ensure that plants don't grow in only one direction. Plants will be healthier and more robust if the light is better distributed. The only other adjustment to make is to raise or lower the height of the grow lights above the plants. A thousand watt total light output needs to be two feet or higher from the plants. Six hundred watts of light needs to be around a foot and a half away; 400 watts should be one foot away; and 250 watts should be about eight inches from the plants. The lights should be run 16 to 24 hours per day depending on how much light the plants require. Sun-loving plants need more, but even plants that tolerate less light will need at least 16 hours to compensate for the lower growing spectrum light of standard flourescents or LEDs. Full Spectrum lights may require the least amount of time. Consult manufacturer's instructions for exposure times.