Home > Great Big Greenhouse Blog > June 2013 > Go Ahead And Close The Blinds

Go Ahead And Close The Blinds

Plants need light…natural or artificial…in order to photosynthesize, a process in which plants use energy from the sun to create food (carbohydrates, fats, and proteins--from which they grow) from raw materials like minerals (in the soil), carbon dioxide (in the atmosphere), and water. Not only do we get to eat the plants, or at least the surplus foods they create by way of leaves and fruits, but we get to breathe the oxygen this process releases into the atmosphere.
 
Just as you supply the necessary water and minerals (fertilizers) your houseplants need to grow, you have to supply the light energy. If you don’t have big sunny windows (and many of us do not), you can use artificial light sources to supplement or replace natural light. To do this successfully, you need the right kind of light, the right proximity to the plant, and the right length of time the light is available on a daily basis.
 
The kind of light (light quality) refers to the part of the light spectrum that the light source (natural or artificial) provides. Light intensity refers to the amount  or strength of light, and light duration indicates the length of time the plant is exposed to the light. In nature, light quality, intensity and duration fluctuate due to factors such as weather (cloudy or sunny) and time of year (short winter days vs. long summer days.) 
 
Anyone who has played with a prism knows that different wave lengths produce different colors—that beautiful rainbow. The different wave lengths aid in different processes within the plant. Natural light provides a lot of energy from violet wave lengths at one end of the visible spectrum to red at the other end. Full sun plants are adapted to thriving with all of this light. Many foliage plants are native to shady conditions, and are adapted to higher levels of blue and green wave lengths with lower levels of red.
 
Artificial lights such as fluorescent tubes (including plant lights), incandescent light bulbs, mercury vapor, metal halide, and high-pressure sodium lamps, all provide differing qualities of light. They also vary in price and operating costs, as well as in the overall appearance (color effect) they give to walls, furniture, and skin tone. For instance, incandescent light bulbs produce more heat than fluorescents do (plants should not be placed too close), and they do not last as long. They are popular for their low price and availability, the fact that they can be used in most home light fixtures, and they produce a pleasant glow. They are not the best choice, however, for plant growth.
 
Mercury vapor lights, metal halide lamps and high-pressure sodium lamps can all be used for supplementing natural light, but draw-backs include high cost, poor ambient color quality, or limited fixture options. They tend to be used more in commercial applications.
 
Fluorescent lights are popular for their efficiency and long life. Regular cool-white and warm-white fluorescents do a good job of supplying adequate light for most foliage plants. They produce mostly blue, green, and yellow wavelengths. They are not the best choice for flowering plants, however, as they do not produce enough red light. So-called “plant” lights (e.g., Gro-Lux and AgroBrite) have an added amount of red light, and are ideal for replacing or supplementing natural light in the home.
 
Light intensity can be controlled by placing plants closer to or further from artificial lights based upon their specific light requirements. You’ve probably seen an African violet stand where the plants are less than a foot from the light source. The type of artificial light you use will determine how close the plant needs to be for the desired intensity. Fluorescent lights are generally lower in intensity (energy output), and so plants can be placed closer to the lights. For example, you are not likely to burn a small philodendron by setting it on the kitchen counter with fluorescent lighting under the upper cabinets.
 
The last element to consider in replacing or supplementing natural light is duration. Most foliage plants come from areas where day length varies little throughout the year, averaging about 12 hours a day. Thus leaving the light source on for half a day is adequate for most houseplants. If you are supplementing for less than desirable natural light, you may want to leave the artificial light on longer than 12 hours. To a certain extent, you can make up for a lower light intensity by adding to the duration. Flowering indoor or seasonal plants like begonias and miniature roses can be moved closer to a light source and/or be given a longer day.
 

The hardest thing about using artificial light is finding fixtures that fit into your home’s d├ęcor. You can purchase attractive (but usually pricey) fixtures, from single lamps to shelving units, or you can build your own light stand using inexpensive shop lights. A softly glowing stand of foliage or flowering plants can add a warm touch to your interior environment.

Posted: 6/6/2013 by Margot | with 0 comment(s)
Filed under: MargotGunn, TheGreatIndoors
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