As a general rule, plants grow best when they can receive at least a couple of hours of direct sunlight each day. Unfortunately, this is not always feasible when growing indoor plants. Many offices keep plants in their buildings to help circulate airflow and brighten up the room, and the plants aren't always near windows. Using heat lamps to grow plants inside can help them receive the light and heat they need, as if they were outside.
Types of Light
There are two types of artificial lighting that can serve as heat lamps: fluorescent lighting and incandescent lighting. Each has its own advantages, and you will want to choose depending on your planting needs.
Fluorescent lighting uses less electricity than incandescent, and the bulbs put off less heat. This means that you will be able to put the bulbs closer to the plants (a great space saver for small offices), but you may need more bulbs to achieve the appropriate level of heat.
The Orchid House nursery at the University of Waterloo recommends that fluorescent lights be changed every six months, or at most every year, as they gradually decay and stop putting out enough light.
Incandescent light burns hotter than fluorescent light, which means that you will not need as many bulbs to generate heat. These bulbs run more of a risk of burning the plants, and so need to be kept further above the plants.
Generally, most indoor plants or house plants grow best when their temperatures are kept between 75 and 80 degrees Fahrenheit. If you plant your own seeds, temperature recommendations will often be featured on the package; this will let you know the best temperature for your plant.
Keep a thermometer in your plant's soil while it is under the heat lamp. You can turn the light off if the temperature gets too high, or add another bulb to the fixture if it gets too low. Tracking and regulating the temperature will reduce the chance of the plants being stunted, or of drying out.
Keep the soil moist to avoid the plants getting dehydrated by the heat. If you notice drying or burning on any of the leaves, provide more water or adjust the position of your heat lamps so that the plant is not harmed.
Generally, fluorescent lights can be placed as close as 8 inches from the top of a plant. Incandescent lights burn hotter, so place them at least 16 inches above the plants. The position can be changed to regulate temperature or moisture in your plants.
If at all possible, get the plant near a window so that it can receive some natural light. The plants will grow under heat lamps, but may not be as healthy or live as long without natural light.
If you have any questions regarding light, temperature or moisture requirements for your individual plants, contact an expert at a local garden center or nursery for advice.