Germination Box For Seed Starting

I am finally trying Steve Solomon’s idea of using a germination box for starting seeds indoors.  This tip comes from his wonderful book on vegetable gardening, entitled Gardening When It Counts, which I highly recommend.

You basically use the germination box to create the ideal microclimate in your house for getting seeds to germinate.  If you look on the seed packet, you will notice that they give germination temperatures most suitable for the seed.  It ranges from 75 to 80 degrees, and so this is the temperature that you are trying to consistently maintain inside your germ box.

We set this up from very humble materials.  You will want, ideally, some type of wooden box that will hold your four-inch pots of seeds.  We had an old drawer from a dresser that works well, but any wooden box that is not too heavy will do.  He says you can even use a cardboard box, but that sounded a little dangerous to me in light of the fact that you will have a light bulb placed directly beneath the box, but it you use a small, like a 25-watt bulb, he says it is okay.

So, you now have a wooden box.  You will want some type of lid that is clear for the box.  Plexi-glass would work well for this, but I didn’t have any, so I used a piece of bubble wrap and just laid it over the top of the box, and it works fine.  You want to be able to open or close this lid to not only put your containers of seeds inside, but also to adjust the temperature.

You will also need a thermometer.  Please use an outdoor house air thermometer, which you can get for less than three dollars at a hardware store, and not a food thermometer, which I attempted to use at first.  (We won’t talk about that!)  Use tape to tape the thermometer to the inside of the wooden box.  Now you have a means for determining exactly what the temperature is inside the box.

Now you need a heat source to go under the box.  Seeds germinate best with bottom heat, and for this purpose you will need one of those ceramic light bulb fixtures that are available at the hardware store inexpensively, a couple of screws that fit the holes in the light bulb fixture, a little square of scrap wood, an electric drill with a bit to fit the screw size you are using, and a screw driver.  You will also need to purchase light cord, and a plug-in.  You have to attach the cord to the light bulb fixture, which is not too super difficult to do, so afterwards you can screw in a light bulb and plug  the cord into the wall, and the bulb will light up.  After it is wired, attach the fixture to the scrap of wood, and the light is now ready to use.

Now you will want to raise your wooden box up off the table so that you can fit the light bulb fixture underneath the center of it.  I had some styrofoam pieces lying around that worked well for this, but you could use bricks or anything that is sturdy and flat to lay the box on top of.

Once the box is raised, you will want to put a light bulb in your light bulb fixture, position it under the box, and turn it on.  Place the plexi-glass or bubble wrap over the top of the box, and leave it alone for a while.  When you come back, remove the bubble wrap and see what the internal temperature of the box is.  You want it to hold at exactly 75-80 degrees–not colder, or the seeds won’t germinate, and not hotter, or the seeds will cook and not germinate.  You can try starting with a 25-watt bulb and if needed, move up to a 40-watt bulb.  You can also reduce the heat by only partially covering the top of the germ box and leaving part of it open.  I found for a small dresser drawer that I used a 40-watt bulb and kept the box covered all the time to maintain a good consistent temperature.

Now you are ready to get your containers and fill them with seed-starting mix (Steve Solomon recommends making your own from 1/2 of  a 5-gallon bucket full of garden dirt, 1/2 of the same bucket filled with peat moss, and 1 cup of complete organic fertilizer, all mixed together well).  Dampen it, put it in the containers, and then put your seeds in the containers, covering with a bit more soil if needed–the seed packet will tell you how deep to plant them.  In the germ box I have, I found that I could fit in 8 four-inch pots, but this will vary depending on the size of the box you are using.  Put the containers in a plastic bag, seal the bag, and then place them in the germ box.  Cover the box if needed, and then you are done.  Check back starting in three days, and every day thereafter, and when you see some of the seeds have germinated, take them out of the germ box, remove the plastic bag, and continue to grow them on under lights.

You can save yourself having to do a lot of transplanting of little seedlings if you only plant one to three seeds in each container, and then thin the plants as they grow to the strongest one and let it grow on.  So far, I am starting basil, tomatoes, peppers and will continue on to eggplant seeds.

This method is working great–my basil germinated in only three days, and the tomatoes in four days–quickest it’s ever happened for me.  I’ll try to post a photo of this soon!

Feel free to leave a comment–do you have any tips that have worked well for starting your seeds indoors?  I’d love to hear about it!



  1. March 25, 2010 at 3:58 pm

    […] pieces, and then put them in sealed plastic bags in a warm spot–my germination box–see this link for a description of what a germ box is.  We will see how many days it takes for them to develop a […]

  2. March 20, 2011 at 5:11 pm

    […] Did you ever start seeds in a self-made germination box? How to build such a box: […]

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