Artificial Light Can Perk Up Houseplants

With short days, sunlight is at a premium. Even houseplants know it. Mostly they just sit and wait for better growing conditions. But if you like to see your houseplants continually bursting into new growth, even flowering this time of year, give them artificial light.

The two common types of light bulbs, fluorescent and incandescent, each emit a different spectrum of light. Fluorescent light is rich in blue and “near-red” (the shorter wavelengths of red light), important for healthy foliage. Incandescent light is rich in “far-red,” important for flowering.

Plants can be grown to perfection indoors with a combination of run-of-the-mill, cool-white fluorescent bulbs and regular, screw-in incandescent bulbs. A good balance of light is achieved with one 15-watt incandescent bulb for every 40-watt fluorescent bulb.

Plant growth is almost as good if you use fluorescent bulbs alone, especially if only foliage houseplants are grown. But the addition of incandescent light makes plants more pleasant to look at.

Plant growth under lights is limited more by light intensity than by its spectrum. The unit of measure for light recalls the days before electricity: one foot-candle (abbreviated fc) is the amount of light a foot away from a candle. For comparison, on a sunny day, plants are showered with 10,000 fc. On a cloudy day, 500 fc.