Artificial light for indoor gardeners can be a mystery. Should you use fluorescent or incandescent? How many watts do you need? Larry Mason, host of HGTV's Winter Gardening, explains what you need when natural light isn't enough. Plants such as African violets and begonias need artificial light during the winter months. Grow lights are eight times stronger than light coming through a window in midafternoon on a cloudy day, and they won't burn foliage. When you grow plants under an artificial lighting system, it's beneficial to provide a humidity tray. Any shallow waterproof container filled with marble chips or light-colored gravel will work to collect runoff water so it can evaporate and benefit the foliage. Warmth from the lighting unit will encourage evaporation. If you're growing only foliage plants such as pothos or aglaonema, incandescent lightbulbs, which provide cool or warm white light, are sufficient. Flowering plants, however, need a full-spectrum light source. If you've ever taken color photographs under fluorescent light, you'll notice that they have a greenish cast because fluorescent light falls between the yellow and green part of the spectrum. Plant leaves reflect green light and absorb the other colors of the spectrum. To encourage plants to bloom, you must provide full-spectrum light, which is simulated by grow lights. Too much or too little light can affect your plants adversely. Too little light will cause them to become leggy and weak, with floppy stems and small leaves. Too much light will cause leaves to curl under and may burn foliage if the light source is too hot. If you use an artificial light source, keep the bulbs 6" to 12" from plants.
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