One of the main benefits of artificial light is that you can control how many hours of light per day your plants receive. This way, those living in northern or southern latitudes can provide their plants with light for growth and development even when the sun sets early, in essence tricking the plants into believing that it is summertime and that they should continue to grow rather than become dormant or, in the case of annuals, die. In addition, your plants will receive constant direct light for as long as you leave the lights turned on.
Although affordable, incandescent lights provide little of the blue-spectrum light essential to plant growth. They are less efficient than other artificial lights as they produce less illumination while utilizing more energy. To draw the most benefit from an incandescent light, you would have to place it close to your plants, and because incandescent lights produce more heat than other types of bulbs, this would likely result in burning your plants. Incandescent bulbs also have very short lives.
High-Intensity Discharge Light
High-intensity discharge lights produce far more illumination while using much less electricity than incandescent bulbs. In addition, while they produce a considerable amount of heat, you can hang them twice as far away from your plants as you would an incandescent bulb, so burning of the plants is less likely. High-pressure sodium lamps emit much red-spectrum light and little in the blue spectrum, making them ideal for greenhouse flowers to supplement natural sunlight and encourage blooming. Metal halide bulbs emit more blue-spectrum light, making them perfect for indoor growing operations for plants that will not flower, such as decorative plants and herbs. HPS bulbs last 12 times longer than incandescent bulbs, and MH bulbs can last five times as long.
Fluorescent Light
Fluorescent lights produce less luminosity than high-intensity discharge lights, though far more than do incandescent bulbs. Fluorescents also produce very little heat and can hang very close to your plants. Bulbs rated in the higher Kelvin temperature range (5,000 to 6,500) emit more blue-spectrum light and those in the lower range (2,700 to 3,000) emit more red-spectrum light, although both also provide full-spectrum light in lower intensities. Compact fluorescent lights will last five times as long as incandescent bulbs, and the straight T-5 full-spectrum fluorescents will last 10 times as long.
Artificial light, if it is an ordinary room light, will only support low-light tolerant plants. Most artificial light sources (fluorescent and incandescent) do not provide the full visible light spectrum that is required by plants for optimal growth, this results in plants that are tall and spindly (etiolated) and sometimes discolored.
However, there are special lights with a spectrum that is tailored for growing plants. They have to be on for longer hours than sunlight, but as long as a plant is getting enough light-energy to manufacture its food, it will grow well. It doesn't matter whether that light is coming from the sun or from grow lights.
The downside to extended exposure to light is the plants metabolic functions operate twice as hard for the same amount of output. Recent studies have also highlighted some of the negative aspects of extended photosynthetic periods (extended light reactive period and shortened dark reaction period).
There are times when artificial light has an advantage.
Hydroponic gardening with artificial light makes it possible to grow plants in unreliable climates that are lacking in sunshine - think of the long "night" periods of areas of the northern hemisphere. In some places in Canada forage for animals is produced indoors during the winter months in artificial conditions.
Supplemental lighting is used in horticulture to produce plants in flower outside of their normal flowering period. For instance Christmas cactus, poinsettias, tulips, narcissus, chrysanthemums, etc.
Many houseplants grow better under artificial lamps, not because of the lights, but because it keeps them away from drafty windowsills!
Plants will grow better under sunlight; artificial light lacks the complete spectrum of light provided by the sun. You can purchase "grow lights" which have a special coating on the bulb to produce more light in the spectrum that plants need to photosynthesize. However, they can never completely duplicate natural sunlight. Artificial lights are produced to help humans see in the dark, so they only need to produce light in the visible spectrum. The sun, a torch, and a light bulb all emit energy in the form of particles called photons. The photons from the sun are a product of thermonuclear fusion. A torch uses a chemical reaction to burn. A light bulb converts electricity to photons. But a photon is a photon – and light is light – whether it comes from the sun or a flashlight.
Vastly more energy comes from the sun than from any artificial light. But the light from the sun is different from a street lamp another way: most artificial light doesn’t emit as much energy in the red and blue region of the light spectrum as sunlight does. In other words, different ratios of reds, yellows and blues all combine together to make up white sunlight. Researchers can successfully grow plants using only artificial light in growth chambers. But sunlight is best for most plants. It’s generally more intense than artificial light, and it’s pretty equally distributed among the different wavelengths that earthly plants have evolved to like best. And there’s another difference between lamps – even “grow lamps” – and sunlight. Grow lamps need energy to light
