Standard fluorescent lights, even those right off the store shelf, are good for seedlings and low light foliage plants. Nonetheless, fluorescent lights generally can't deliver the strong light needed to grow plants much taller than 6 or 8 inches. Fluorescent lights are popular because they are inexpensive a do not heat up, allowing the light to be extremely close to the plant without damaging it. The closer the light, the more benefit to your plant. Fluorescent grow lights are some of the most commonly used lights for indoor gardening. If you are growing vegetable or flower seedlings under a standard two-bulb fluorescent fixture, you can usually achieve a good color balance by combining one cool white and one warm white bulb.
Metal halide and high pressure sodium plant lights are the most efficient and productive lighting system available to take plants from seedling all the way to maturity. Metal halide lamps emit cool blue/green/violet light, simulating daylight. High pressure sodium lights supplement halide lights with red/orange light. Experts use metal halide lights for a plants growing cycle, then switch to high pressure sodium lights during the blooming and fruiting phase. Used in street lighting and industrial use, these bulbs provide a huge amount of light.