Building a Seedling Tray with Grow Light

To those of you out there committed enough to growing plants from seeds, I salute you. While I find it harder than sticking a grown plant in the ground, I also find it many times more rewarding.
I've grown plants from seeds for a couple years now with mixed success and a general sense of improvement. The biggest boon to my efforts was a growth light/seed tray that we built. I know there are similar things out there that you can buy pre-made. We decided to make our own because we had a very particular space it needed to fit in. You can choose whatever works best for you.

Windowsill seed tray and growth light.

As you can see in the picture, this particular tray sits in our windowsill. That way it serves as a great seed starter in the spring and a plant tray throughout the winter.

Materials you need:

• 15 feet of 1x3" cedar boards
• An 18"x36" sheet of 1/8" thick plexiglass
• Hammer and nails or a nailgun (We used a nailgun)
• 24" two-bulb fluorescent light fixture
• 2 24" fluorescent grow lights
• 10 (approx) adhesive padded feet
• 16 Counter-sunk screws

Step by Step:

1.   The dimensions are 3 feet long, 18 inches wide, and 16 inches tall. Cut your wood to the following dimensions:

• 2 pieces at 36 inches (3 feet) long, with mitered ends. These are the long edges of the frame.
• 2 pieces at 18 inches (1 1/2 feet) long, with mitered ends. These are the short edges.
• 2 pieces at 16 inches long, with straight edges. These are the uprights.
• 1 piece at 36 inches (3 feet) long, with straight edges. This is the top log piece.
• Technically, you en up using 14 feet and 8 inches total, but some is lost in the cutting and the leftover bit is pretty minor.

2.   Assemble the base first using the 4 lengths with mitered ends. We used mitered ends (cut at a 45 degree angle) for ease of measurement and attachment. You can use straight edges if you prefer, but make sure you adjust your measurements to take that into account. We used three nails at each corner to secure the base. This seems flimsy, but once everything is assembled it becomes very sturdy.

 3.   Attach the uprights. Measure to the middle of the 18" base piece. Make sure you are at the exact center or your cross piece will not line up in the next step. The uprights attach to the outside of the base and line up flush with the bottom edge. As you can see in the picture, we used about 5 nails to secure the base of each upright.



4.   Attach the upper crosspiece. Attach the 36" flat ended crosspiece. It attaches to the inside of the uprights. Make sure your ends and flush for a more finished look.

5.   Attach the plexiglass base to the bottom of the frame. You want to use screws with a counter-sunk head. That means they have a V-shaped head when looked at from the side. This helps evenly secure the plexiglass without cracking. More importantly, the screw head itself sinks into the material. This prevents the screw head from sticking out and scratching your table/counter top. We used 16 screws (5 on the long sides, 3 on the short). We then added some adhesive padded feet to ensure that the base would not scratch our windowsill.

6.   Attach your light fixture. You can choose whatever type of light fixture you wish. We chose a 24" fixture that holds 2 fluorescent grow light tubes. Ours came with a 10 foot cord with an in-line switch, but every one is different. Shop around before you make your final decision and don't be afraid to ask the aides at the store for some suggestions. They can also give you advice on installation if you're unfamiliar with that.

 7.  Some final pointers:

I chose to work with cedar because it is lightweight and resistant to warping and decay. I know that this frame stays indoors and is relatively dry, but since it's around some water it was a better choice for longevity. You can use whatever wood you want, but I suggest some research first.

I wanted a plexiglass bottom because it is sooo easy to clean up. Again, not that I expect to have water everywhere, but it was better to play it safe. You can try alternate bottoms, but realize that this is the part of the frame most likely to get wet. I might try adding a sealant to waterproof things.

Some people use a heated pad for starting seeds. I don't, but if I ever do, I prefer the heating pad not to be directly on wood. This is another reason I went with plexiglass. Alternately, you can raise the frame up on legs if you want a space underneath for a heating pad.

And you're done! This setup works fantastic for myself, and I hope these plans can help you design your own.