How To Make Inexpensive Seed Starting Lights

I have been looking for the perfect DIY seed starting setup for a few years. I tried the popular shop light on a homemade stand version and found it was not enough light. All of the plants stretched toward the middle of the tray. I tried windowsills but no larger windows in my house face the right direction to get enough light so I had sad, stretched out seedlings again. I looked at seed starting lights online and was put off by the prices as well as the bad reviews on so many of them. This is by far my favorite and I'll be adding on to this next year for even more space.

Each shelf has a separate cord and each cord will run about $60 including bulbs and take about 5 to 10 minutes to make. I can fit 2 standard 1020 trays per shelf. The bulbs give off a small amount of heat which is the perfect amount for the trays above and makes heat mats unnecessary. I keep everything plugged into a power strip so I have one switch for all the lights which makes turning them on and off very easy.

I'll add links for the items I used but there are probably comparable versions at your local hardware store. I already had the shelf that originally came from Costco. I don't remember how much it was but there are inexpensive versions in many places. For one shelf, you will need 1 lamp cord, 4 lamp holders, 4 twin socket lamp holder adapter and 2 small wire nuts (we had some of these in our home improvement stash but they are very inexpensive and at every hardware store). For tools, you will need something to mark the cord, a utility knife and wire strippers. Be safe, never plug the cord in until the project is fully assembled.

Measure your shelf to decide how far apart your sockets will be on the cord. I made mine 10 inches apart and about 6 to 8 inches from the end. Mark the cord where the sockets will go.

The cord has two wires inside, one is hot and one is neutral. The edge of the hot wire is smooth and the neutral is ribbed.

neutral (ribbed) side on the left and the hot (smooth) side on the right

Using the utility knife, carefully split the wires apart at each marking. Be careful not to cut through the rubber insulation around the wire, just through the groove up the center. Once you make a slit, you can pull the two sides apart to widen the opening. Make the opening just wide enough to fit on the socket.

Unscrew the top of the sockets. The pins have different metal colors. One is silver and one is brass. The hot (smooth) wire goes on the brass pin and the neutral (ribbed) wire goes on the silver. In the picture below, you can see the silver on the left, brass on the right.

Use the wire strippers to cut through the insulation on both sides of the wire at each marking. Use the 16 or 18 gauge mark on your pliers if they have them. Put the wires on the pins (double check that the correct wire is on the correct pin) and line up the snips in the insulation with the pins then screw the cap on.

Put the two wire nuts on the two exposed ends of the wires using one nut per wire. Do not put these together in one wire nut, they need to be separated.

Screw the twin socket adapters into the sockets and add the bulbs. These are the bulbs I used and using LED bulbs only is important because they have lower wattage and temperature. You can mix colors of bulbs if you would like but I used all daylight. I wanted more cool light than warm as I'm not trying to get anything to flower yet, only build healthy roots and stems. I used 100 watt equivalent bulbs for the brightest light possible. Hook the cord to the shelf above and you are finished!

Next year, I may look at finding something to enclose the shelf so less light and heat escape but it works very well as is so I'm not very motivated for that project. My seedlings this year have been great. None of the legginess like previous years has happened and I already have 4 inch tall tomatoes in the greenhouse as of early March.