Many plants do well indoors in natural light, but some tropical plants---and tiny seedlings---need more intense light from special lamps. Most herbs will survive in natural indoor light, but they will grow only if they get supplemental light that provides the color spectrum they need. Small indoor plant lights are not expensive, and maintaining an indoor garden can be very satisfying.
The seeds of some plants actually need light to germinate. All seeds need light to grow. This lighting can be very simple and inexpensive---24-inch or 48-inch fluorescent tubes in a plain fixture such as a shop-light. Like all plant lights, the fixture must be adjustable so the lamp can be kept a few inches from the plants as they grow. Hanging the fixture on chains, from a hook in the ceiling, is an easy way to do this. The light can be moved up or down one chain-link at a time. In a two-lamp fixture, use one cool-white and one warm-white tube for best results.
Single Plant Lights
Some homes have large indoor plants that need extra light, especially during the darker winter months. This is easily provided by an Agrosun Day Spot incandescent lamp. A really large plant or small tree would do better with a more powerful mercury vapor spot grow bulb made by Wonderlite, which provides the correct balance of blue, red, and far-red wavelength light needed. These lamps screw into just about any fixture, from a cheap clamp-on to a recessed fixture.
An indoor garden can grow happily under a compact fluorescent lamp (CFL) fixture, such as the Hydrofarm Compact Fluorescent grow light system. The attractive white rectangular reflector would not look out of place in a well-furnished home. Two lamps are available: a full spectrum daylight version that is good for most houseplants, and a full spectrum warm version that has more red and orange that supports the fruiting and flowering of indoor plants.
High Output Fluorescents
High Output (HO) fluorescent tubes and their special fixtures put out twice as much light as standard fluorescent grow tubes. This is a very bright light that is ideal for starting seeds, growing herbs and leafy vegetables, and really comes into its own for the intensive propagation of cuttings and the growth of African Violets. These tubes are available in 24-inch and 48-inch lengths; fixtures hold two, four, six or eight tubes.
High Intensity Grow Lights
Many plant lights will maintain a plant, and may provide enough light to allow small plants to grow a little. To actually grow sub-tropical plants such as tomatoes and peppers all the way to fruiting, High Intensity Discharge (HID) lights are required. They produce about 500 percent more light than a normal incandescent grow bulb. They require special fixtures, and the light sources include high-pressure sodium and metal halide. Leading manufacturers of these lights are Sunlight Supply and Hydrofarm.