Posted by: Kim_Hamilton on 11/18/2009 11:31 AM
Updated by: thepinetree on 11/19/2009 09:18 AM
Expires: 01/01/2014 12:00 AM
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How to help your houseplants during the winter~by Ken Churches
Light is one of the most essential factors for houseplant growth. But, on a foothill winter day, light levels may be only 30 percent of what they are on a sunny summer day. What should you do? Light intensity influences the manufacture of plant food, stem length, leaf color and flowering. For instance, a plant grown in low light tends to be spindly with light green leaves. A similar plant grown in bright light would tend to be shorter, better branched and have longer, darker green leaves.....
The distance the plant is from the light source and the direction a window faces determine the light intensity a houseplant receives. Southern exposures receive the most intense light. Western and eastern exposures get about 60 percent of the intensity of southern exposures. Northern exposures get only 20 percent of the light of southern exposures. Most of the light coming in north windows is indirect light.
Other factors influencing light intensity besides season include the presence and type of curtains, cloud cover, shade from buildings or vegetation, the cleanliness of the window and the reflectiveness of the surroundings. Houseplant owners can compensate for low light intensity by increasing the time a plant is exposed to light. Increased hours of lighting allow the plant to make sufficient food to survive and grow. Additional light can be supplied from either incandescent or fluorescent lights or special horticultural fluorescent lights. Any type of light that burns a metal element, including the common household light bulb, is incandescent.
Incandescent lights produce a great deal of heat (red spectrum) and are not very efficient users of electricity. However, they provide the red spectrum of light for plants. Florescent lights are cool or blue light. A combination of fluorescent and incandescent lamps supplies the best light for houseplants. Cost-wise, using only cool white fluorescent tubes provides the best light for the money. Special “plant growing” or “grow lights” are fluorescent tubes that make plant foliage and flowers appear more attractive, but they are more expensive than the cool white tubes, and in general, the plant growth may be no better.
Fluorescent fixtures should be suspended about 24 inches above plants. If you use incandescent lights, check the plants three times a day for the first two days to make sure the lights are not too close. Day length or duration of light is also of some importance to some plants that are sensitive to day length, including poinsettia, kalanchoe and Christmas cactus. Most flowering plants are not very sensitive to day length. But, all houseplants need some period of darkness and should be illuminated for no more than 16 hours.
This article adapted from Cooperative State Research, Education and Extension Service, USDA. Please contact the Farm Advisor’s office at cecalaveras.ucdavis.edu or 754-6477 with your agricultural questions.
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