Monday, January 17, 2011

Build an indoor seed germination chamber

I read that today, January 17th, is statistically the saddest day of the year. I'm not sure exactly how that was quantified, but few people in Missoula will likely disagree today. It is about 40 degrees and raining outside. Although this is not unheard of for a January thaw, it is definitely pretty dreary today. On the bright side, with all the melting snow, it is a good day to marvel at the beach lines on Mount Jumbo and Mount Sentinel.

Givin the dreariness, I thought this would be a good day to write about a garden project that you make and have inside. This is post is about building an inexpensive seed germination chamber.

This is a fun project and it is really cheap to build (especially if you get all the materials at, say, Home ReSource (1515 Wyoming Street in Missoula). But even if you don't live in Missoula and you have to pay big city prices, you will hardly be out any money.
It is timely to think about ordering seeds and starting them indoors. We just inventoried all our seeds for the vegetable garden, did some planning and deliberating, and last Friday all the seeds arrived. We'll be transplanting many of our germinants out in the greenhouse; if you don't have a greenhouse, consider building a cold frame to get a jump on spring. After the depressing weather the last few days, it is really important to think of spring and remember that it is in fact getting closer every day!

We use our germination chamber for starting vegetables, but of course you could use yours for starting native plants.

Here I will show what materials you'll need to make a germination/ growth chamber, but really
it is nothing more than a box with a light in it. Here are some tips:

If you haven't been before, take this as an opportunity to visit Home ReSource, a building materials reuse center. Home ReSource is my favorite place to shop and come up with ideas for my next project, and it is where I get materials for many of the things I've featured on this blog from my greenhouse to my bee house.
Below is Lauren, the co-founder and co-director of Home ReSource. He and any of the other enthusiastic, knowledgeable staff enjoy helping customers, especially in the treasure hunt-like environment of Home ReSource.
To start, select a fluorescent light fixture. Show below are an assortment of recycled fixtures that cost just a couple of dollars each. Whatever size you select will dictate the size of the box you build. I use a standard 4' "shop light" set up.

The next step is getting bulbs for the fixture. Although you can buy "grow" lights (lights specifically for growing plants) you do not need to.
All you need are fluorescent bulbs that cover the range of the light spectrum, and you can accomplish that with one "cool" bulb, and one "warm" bulb. At Home ReSource, the bulbs are cheap ($0.50, for a 4' bulb).
But even if you buy a new bulb and it is a "grow" light, they are still not terribly expensive.

The bulbs not only provide light for the plants, they also supply the heat for germination and growth. Although a florescent bulb does not give off much heat, it does give off some, and that will be plenty to keep the chamber around 70 degrees, especially with a well insulated box (see below).

The next step is selecting a timer. You want to set the growth chamber so your plants will get 12 hours of light/ day. Again, a trip down the aisles will reveal several timer options.
Here, for example is a new in the box timer for $4.
But if you didn't want to spend that much, there are plenty of other options. Look at the piles of timers laying around at Home ReSource...
The next step is building the enclosure or box. The simplest way is to make a box out of rigid insulation. Insulation with a foil face is best- it allows light to reflect. However white rigid insulation will do just fine. The thicker the insulation the better. The thicker it is, the more rigid the box will be and the greater the insulating value.

Just build the box to allow for the size of the light and the size of the trays you might use for seed starting. In general you want the box to be small, for conserving heat, but you have to allow the light fixture to move up and down.
So the plants don't get leggy, you want the light to be about 1" from the plants at all times, so allow for some space to adjust the fixture height.
Using the rigid foam insulation is a really easy way to build the box- no complex joinery to deal with. I made ours just using foil tape to hold it together.
It is nothing fancy, but it works, and has lasted several years taking up some unused space under our basement stairs.
The good news is, June 17 is statistically the happiest day of the year, and it will be here before you know it, with a whole bunch of plants you started from seed this winter.


  1. I like your statistics. Especially about June.
    Almost time to start some seeds here. Good advice.

  2. Very nice setup! I use the lights and shelves, but have never put it in an insulated box before - great idea.

  3. Its really fantastic Blog.LED Grow Lights are one type of light used to do this. Even though using these grow lights for a "hobby," i.e. growing your own food and such, are in their infancy, they are becoming more and more popular.

  4. That is a great project you have! I want to try growing some of my plants indoors when I get more space. But will take note from your example.

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