By Evan Cutler
Special to the Turnagain Times
Last issue, I shared a bit of the vision for a year-round food production facility here in Girdwood. To grow plants anywhere on earth, you need at least four things: seeds, nutrition, proper temperatures and light.
In this article we will explore the issue of light.
Depending upon whom you ask, the shortest day in Girdwood, Dec. 21, may be about four hours and 20 minutes long. In any case, it's too short for growing harvestable vegetables in winter. If we want to be growing plants to produce food year-round, we will need to use artificial light to supplement what is naturally available.
The visible portion of the electromagnetic spectrum for most humans ranges in wavelengths from around 400 nm (violet) to 700 (red) nanometers. When sunlight is sent through a prism, or a misty sky, to separate the light in order of wavelengths, we interpret these frequencies as a rainbow.
Gardeners have been using full spectrum grow lights to grow everything from tomatoes to marijuana indoors for decades now. This technology works fine, but it results in a very expensive electric bill because those lights burn hot.
While humans need full visible spectrum to see, plants can grow very well with just a few colors of light. It turns out that plants are sensitive to a few peak ranges in the blue, yellow, orange, and red parts of the spectrum, and that they need a different balance of these light energies during different parts of their growing cycle. There has been quite a lot of scientific research in this area lately.
The past few years have seen a wave of new breakthroughs in the design and production of Light Emitting Diodes, known as “LEDs.” It turns out that they are now being mass-produced with increasing efficiency and will ultimately become less expensive to manufacture than traditional lighting.
What's really interesting is that LEDs can be made to emit the specific wavelengths that plants need to grow.
By using LED lights in the Sustainable Girdwood greenhouse, we can provide all the light our plants need, and none of what they don't need. Better still, they require a fraction of the energy traditional grow lights need, so we won't need as much electricity to grow our plants. LEDs are part of our path to making Girdwood Sustainable.
We hope you will join us at our public meeting in the Girdwood Community Center meeting room (library building) at 4 p.m. this Saturday, Nov 21.
Evan Cutler is a facilitator for Sustainable Girdwood.
