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Friday, February 3, 2017
Seedlings grown under too low of light are very poor quality and probably won't survive outdoors. Luckily, we can use supplemental lighting with good results in growing plants indoors.
However, not all lights are created equal. If we make good choices in the type of light, how long the light shines and the distance between the light source and the plants, we can have success in growing seedlings even without the sun.
The type of light we choose will affect the intensity or amount of light. The lights we are most familiar are incandescent and fluorescent. Incandescent or the traditional light bulb is an inefficient light source producing a lot of heat with not much light. With good reason incandescent lights are being phased out. They are also high in red wavelengths, but deficient in blue.
What's this red and blue wavelength stuff? Plants absorb light of many wavelengths, but mostly in the blue and red range. They absorb little in the green range, which is why leaves look green to us.
Fluorescent lights are the most available, most efficient and the most affordable lights to supplement plant growth. The newer smaller diameter fluorescent tubes are more energy efficient than the older wide tubes. An inexpensive shop light of two - 4 foot tubes available at most hardware stores works very well for growing seedlings. New tubes should be purchased each year.
To confuse our choices not all tubes provide the same wavelength. A combination of a cool white and a warm white (also listed as day light) is a good combination for growing seedlings, houseplants and African violets. Special grow lights or full spectrum lights are also available. They provide a more complete spectrum or range of wavelengths. Grow lights are also more expensive than regular fluorescent. For you competitive gardeners the slight increase in growth may be worth the added price.
Because electric lights don't have the intensity of the sun, we generally leave the lights on longer to compensate. However, plants do need some dark. Maximum time for seedlings is about 16 to 18 hours a day.
Distance from the light to the plants affects the amount of footcandles (light quantity) the plants receive. For example, two 40 watt fluorescent tubes 1 to 3 inches from the plants deliver about 800 footcandles. At 12 inches away the footcandles drop dramatically to 250 footcandles. Since fluorescent tubes give off little heat, we can place them close to seedlings, about 4 to 6 inches.
Light is a big part to starting seedlings, but also use a good seed starting soil mix and clean containers. Keep seeds moist. Be sure to read the seed packet to determine the proper time to start seedlings.
Starting your own seedlings indoors for later transplanting in the garden does not have to be difficult or expensive. It's a great way to survive the winter blues and get a jumpstart on spring.