Introduction: Green Thumb Grow Lights

To quickly and efficiently grow plants from seeds I built a simple and low cost LED grow light kit . I used a plastic storage bin to support the LED strip lights and to provide a moist environment during seed germination and early growth. After the seedlings reached a healthy size they were transferred to the garden for the summer.

The figure above shows that plants absorb light for photosynthesis at blue (~ 450 nm) and red (~650 nm) wavelengths. For a typical incandescent light bulb most of it’s light energy is in the infrared spectrum and is wasted.

For my seed starting kit I selected the Gled® red-blue LED grow light strips that are energy efficient and super bright. Additionally, the measured light strip spectrum matches the wavelengths that plants absorb during photosynthesis, promoting efficient and optimal plant growth.

Growing plants from seeds allows you to choose heirloom, organic (not genetically modified organisms) and unique plants that are not easily found at nurseries. Growing your own plants and vegetables promotes healthy living and is fun!

Step 1: Materials and Tools

Here is what you will need for the project:


  • Gled red-blue LED strip lights, ~$30 / 5 strips
  • 12 volt power adapter, 6 amp, ~$8
  • Timer, ~$5
  • Large plastic bin, ~$6


  • Jigsaw or small hand saw
  • Soldering iron


  • Soil
  • Seeds

Step 2: Cut Openings in the Plastic Bin

The first step is to cut openings in the plastic bin to hold the LED light strips and to provide for cross ventilation.

Cut 5 evenly spaced rectangular openings (slightly larger than the light strip cross-section) near the bottom at each end of the bin. These openings will hold the LED light strips in place without any glue or tape.

As shown in the above figures, cut two large openings (mine are ~6 x 12 inches) to provide for side ventilation. During seed germination I covered the openings with plastic wrap. Once the seeds sprouted I removed the wrap to provide for cross ventilation.

For a clean cut, I outlined the desired opening with tape. I used a jigsaw to cut the openings, but any fine toothed saw will work. The side ventilation openings have rounded corners to make the cutting easier.

Step 3: LED Light Strip Wiring

The LED light strips come pre-wired with small connectors on each end.

You can connect the strips in series, one to the other, however I found that the first light strip became fairly hot, given the amount of current flowing through it.

It is best to break the light strips into two groups to reduce the current (and heat) of the first strip. I connected the power adapter separately to groups of 2 and 3 light strips. This way the total current is split between the two light groups, avoiding overheating issues.

I used a soldering iron to attach jumper wires to the power adapter and attached small lug connectors to these and the LED light strip wires. If you wish you can skip the lug connectors and solder the jumper wires directly to the LED light strips.

Step 4: Assembly

Assembly is easy, simply slide the light strips into the bin openings and connect the jumper wires as shown in the above photos!

Step 5: Seed Growing Process

Select your seeds from a variety of local or internet suppliers.

Plant the seeds in seed starting soil, which has been sterilized to prevent fungal growth.

Seeds germinate within 1 to 3 weeks depending on the seed type and should be kept warm and moist during germination.

After seedlings emerge, most require 14 to 16 hours of direct light to produce healthy stems and leaves, which can be controlled by adding a simple timer.

As the seedlings begin to outgrow their container, they should be thinned and transplanted into larger pots.

Step 6: Results

To measure the performance of my grow light kit I planted two basil seed trays. One tray was placed under the grow lights and the other was placed near a south facing window.

About one week after germination, as shown in the the above photos, the seedlings under the LED grow lights were strong and leafy, whereas the ambient light seedlings were a bit spindly.

Step 7: Plant Choices

Growing plants from seeds allows you to choose heirloom, organic (not genetically modified organisms) and unique plants that are not easily found at nurseries. Common and unusual plants that interest me are:

Common Plants

  • Cucumbers
  • Tomatoes
  • Peppers
  • Zucchini
  • Basil

Unusual Plants

  • Large Bottle Gourd
  • Rouge Vif d’Étampes (Cinderella pumpkin)
  • Baby Bok Choy
  • Asparagus Beans
  • Cinnamon Basil
  • Viola Sororia Freckles
  • and many more…

Step 8: Summary

I designed and built a low cost (< $50) LED grow light kit to grow plants from seeds that is simple and fun to use.

The blue-red LED light overlaps the wavelengths that plants absorb during photosynthesis promoting efficient and speedy plant growth.

Growing plants from seeds allowed me to choose interesting vegetable plants for my garden that were not available locally.

I hope that you enjoyed reading my LED grow light instructable!

Thank you, GreenThyme

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