The Cheap Vegetable Gardener

Effects of color spectrums on plant growth

15.9 years ago indoor growbox, LEDs, spectograph

I have written about the importance of lumens when growing indoors but the intensity of the light at specific wavelengths can be over even more important.  NASA has done some significant research on the subject to determine the possibility of growing leafy vegetables on a trip to Mars using as little electricity as possible to get the most benefit out of every watt.  In space any wasted energy (heat or light not used by plant growth needs to be severely limited.

It should not be a surprise that using LEDs is part of the solution they came up with since they use 20-30% of the energy of a comparable HPS (High Pressure Sodium) bulb which is considered very efficient given the lumen output per watt.  The most interesting part of their findings was how specific red and blue wavelengths were imperative to the growth of plants and actually could sustain growth with just these limited wavelengths.  Given the freezing temperatures and masses of snow on the ground the best use of this information for indoor gardening and specifically my $20 PC Grow Box.  Understanding the wavelengths that your artificial lights creates can help you have increased plant growth and save on your electricity bill at the same time.

When evaluating which light you must consider wavelength and also the intensity of the light at that wavelength.  A tool to do exactly this is a spectrograph, which you can purchase, make your own (this was a fun project with the kids), or just trust other peoples readings.  I chose made my own, but am displaying results (led museum) since I would have to estimate the intensity based on the brightness of the spectrum created which would lack some accuracy.

Just to get some perspective, this is what how various light sources appear to a spectrograph:

Sunlight
Florescent Bulb
Incandescent bulb
Low power  blue LED (5mm)
Low power red LED (5mm)
Low power white LED

As you can see incandescent appears to be the closest to matching the wavelengths and intensities of sunlight though it we need to remember that the orange/yellow/green wavelengths provide essentially are wasted from the plant’s perspective due to natural reflection of these colors.  So if a light looks bright to you, there is a good chance you are wasting electricity, as humans our eyes respond well to these wavelengths why we will find these bulbs to be much “brighter” from our perspective.  The fluorescent bulb is a good example where we see this light as bright for plants other than the small slices spectrum much of the light is unusable.  I have had good luck growing indoors with CFLs along with incandescent, but from the information above I my results cold have less spectacular if hadn’t included the incandescent bulb.  At the time the only reason I used it was to generate a little extra heat on some of the cold nights.

The key point is I could easily have much better results using significantly less power.  According to NASA’s research the most efficient configuration is to only have red/blue LEDs consisting primarily of red (80-85%) with the remaining (15-20%) being blue LEDs.  I would recommend replacing the some of the of the blue LEDs with white LEDs to provide a full spectrum including a pretty intensive blue spectrum in itself.  As an added bonus this will provide some “human” light in orange/yellow/green spectrum to allow us humans to view plants with less strain.

By replacing the two 24 watt CFL and one 80 watt incandescent bulb with a few hundred LEDs I could drop at least 124 watts with my new configuration.  Assuming I am running my grow box every day for 14 hours a day this could save me over $45 a year as well as just being the more environmentally conscious thing to do.

So during these cold winter months if you grow indoors whether just for seedlings or vegetables all year round be sure to remember that not all indoor lights are created equal.

Tags: cheap, garden seeds, grow lights, growbox, led, outdoor plants, vegetables

Science Fair: Why don’t strawberries grow during the wintertime?

16.7 years ago indoor growbox, strawberries

My 6 year old daughter was the inspiration for the PC grow box for her science fair project to figure out why strawberries don’t grow during the wintertime. She started by picking a strawberry plant from our garden (snow still on the ground) and we potted it in a terra cotta pot which she carefully painted ahead of time. We put it in the grow box in our garage with the lights on for 14 hours a day. As she saw significant changes in her strawberry plant we took pictures. After about a month of growing we went through the pictures and she wrote her report explaining the changes.

She definitely had a good time standing by her display proudly telling people about her project and answering any questions that the various visitors had. She did take a break to take a look at some of the other kids displays which I took note of the gardening related ones which would be great for a science projects for any of your budding scientists:

– Seed germination (soil or paper towel)
– How plants grow with different color of lights (colored transparent plastic)
– How plants grow when given different liquids (water, soda, milk, vinager, diet soda)
– Effects of being mean or nice to plants
– Effects of music on plant growth
– Hydroponics
– Effects of temperature on plant growth

Tags: cheap, garden seeds, grow lights, growbox, outdoor plants, strawberry plants, vegetables

Cheap PC grow box for less than $20

16.9 years ago indoor growbox

I enjoy when I can be rewarded by overcoming mother nature, so when my 6 year old mentioned she wanted to figure out why strawberries will not grow in the winter for her science project I couldn’t have been prouder. Once she determined the reason was because it was colder and the sun wasn’t up as much, she suggested using lights to help them get more light and warmth.

The next obvious step was to create a grow box, now if this wasn’t cheap vegetable gardener I would just buy a commercial grow box, but by now you should know better than that…

Looking through my garage I found my first victim, an old PC case. After a few screws and a few drilled out rivets I had a good structure for the grow box. Next I added some Styrofoam insulation which I got at Home Depot on all 4 sides (this step is optional if your PC grow box will be inside)  Also at Home Depot I picked up a cheap extension cord, lamp timer, and a socket plug adapters that allowed me to plug right into the extension cord. Followed by a small hole in the top and about 45 minutes my work is done.

In January we had a strange couple weeks of 20 degree days so I also added an incandescent build for some extra light but more importantly little extra heat. Which I made from a old lamp taking up space in the garage. With all the sides up the box is able to maintain a 70-75 degree temperature even with the chilly conditions in the garage.

After a little over a week we seemed to be getting some good results with our first blossom on the strawberry plant my daughter chose under snow in our garden.

Costs for Cheap PC Grow Box

Some of our other grow boxes
Fully automated computerized grow box (Project Everbearing) Beta 1
Cheap LED Light and Grow Box

Tags: cheap, grow lights, growbox, led, outdoor plants, strawberry plants, vegetables