Our climate can make growing plants outdoors difficult or impossible at times. But you can control the environment Indoors, although a vital component of plant growth--sunlight--could present a challenge. There are a number of artificial light solutions to solve this problem; some specialized even for certain stages of a plant's life.
Incandescent and Fluorescent Lights
Incandescent light bulbs are a cheap option for plant-growing lighting. A high-output bulb of 150 watts or more can easily supplement light for most indoor houseplants. The light spectrum of Incandescent is generally considered too narrow--with less of the colored lights needed for photosynthesis--for more than a houseplant or two.
The most commonly used artificial light source for plants, Fluorescent lights, are highly prized for their efficiency and low heat production. Low heat output allows the lights to be placed closer to the plants, which lets the plants use more of the light. Fluorescent lights are most commonly used to grow seedlings. Low-light needing Herbs and other plants that require low light levels can also use fluorescent lighting.
The low lumen (brightness per unit of energy consumed) output of most commonly available fluorescent lighting makes it a poor choice for budding and flowering plants. Recent advances in fluorescent technology have yielded higher efficiency and more compact designs.
High intensity discharge (HID) lamps are an excellent primary light source for plants. While far more expensive than incandescent or fluorescent lights, you get what you pay for. HID Lamps are very efficient, with a single 1,000-watt lamp producing as much light as 50- to 40-watt fluorescent bulbs.
Metal halide lights produce a whopping 125 lumen per watt, making it more three times as efficient as similar fluorescent bulbs. The blue and white color of metal halide lamps makes them excellent for promoting the growth of leafy plants. It's the best substitute for plants receiving little or no natural sunlight.
High pressure sodium lights are the most efficient grow lights available, with a 15% advantage over metal halide lamps. The draw back is that the orange/yellow spectrum of light from high pressure sodium lamps is closer to the sun's output at midday rather than the sun's output in general. For this reason, high pressure sodium lamps are excellent for flowering plants or as a supplemental light.