Agriculture Reference
In-Depth Information
A homemade rack for seedlings works great and costs little.
The fluorescent tubes need to be selected with the needs of
plants in mind. Cool white fluorescents put out more blue
light, and warm white fluorescents put out more red light.
Combining the two in the same fixture gives a perfectly
acceptable mix of wavelengths. It's what I use, and a good
many farmers use it successfully. 34 There are also special
tubes for fluorescent light fixtures that are specifically
designed for growing plants or duplicating the sun's
wavelengths—and these work well too but at a cost roughly
six times higher than regular tubes and at a reduced light
output. The thing to watch for with fluorescent lighting
generally is light output, because plants need a lot of it. Go
with the highest light output tubes that will fit in a 48-inch
shop light fixture. Because the lights are used approximately
five months out of the year, the tubes need to be replaced only
every other year. Replace them even if they look and work
fine, because after being used for two years, their measurable
light output will have declined.
The intensity of light decreases in inverse proportion to the
square of the distance from the source. In other words, the
further away the lights are, the less light the plants will get.
Fluorescent tubes need to be set up so that they are only an
inch or two above the seedlings for them to get enough light.
Because plants grow, either the height of the lights or the
bottom of the plants needs to be adjustable.
Plants need a combination of both light and darkness to
complete their metabolic processes, so too much of either can
be a bad thing. Because even closely spaced florescent lights
are an imperfect substitute for true sunshine, the lights should
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