On our small farm, projects often come about after some internet research and using odd pieces of “junk” we’ve got hanging around. One of this winter’s projects was a germination chamber.
Some of our seeds require light to germinate but most vegetable seeds don’t. They do need consistent moisture though. So, in an effort to reduce the space that seedling trays take up before the baby plants emerge (at which point they do require light) and in order to reduce the watering these trays need so they don’t dry out, many growers use a germination (or sweat) chamber.
Since we moved to this farm, we’ve started our transplants many different ways. Each year, we’ve made some kind of germination chamber and it’s always looked a bit different. At its most basic, we stacked bread trays near our wood stove and wrapped them in plastic to keep the humidity in. Once seedlings emerged, over the years, they’ve been moved to hot beds, our sun porch, and, for the last few years, electrically heated benches in our high tunnel.
A germination chamber is basically an enclosed area, where the temperature and humidity can be regulated. There is often some sort of tray stacking system where it is easy to see which trays have germinated and be able to easily insert and remove trays. Some people have used old chest freezers, but as our only free chest freezer was a little too small for our purposes, we used an old wire rack and former project leftovers. Farm Hack was a good online resource for helping us design our germination chamber.
It all started like this:
A 3 foot wide by 5 foot tall wire rack (sans shelves) and a stainless steel sink.
Ideally I would have taken this in to someone to weld a piece into the bottom of the sink to seal it up (might still do at some point), but opted for the cheaper option of silicone and a sink stopper.
Fortunately, the spacing of the supports for the shelves worked with most of the trays that we use (the 50 cell Winstrips are our tallest trays).
For the shelving I used ½” EMT, (galvanized electrical conduit), and then made a little notch with an angle grinder at both ends to fit over the wire supports. They are easily removed so that the shelf spacing can be made bigger to accommodate the Winstrip 50 cell trays, or to add more than 3 bars per shelf (4 is better for the flimsier trays).
I decided to recess the sink and slope the sides because of comments other builders had made about water pooling on the bottom.
Copious amounts of tuck tape to ensure most of the water finds its way back to the sink and not through to the floor.
Originally, I was planning on using the Durostat prewired thermostat, purchased online from Farmtek/Growers Supply, but procrastinated a little and needed one faster than what ordering one online would bring. Luckily enough, our nearby plumbing and electrical supply place, Eddy Group, carried this dandy cooling/heating thermostat that mostly gets used for chicken barn applications. It ended up being about $20 cheaper (more if you consider having to pay the US exchange rate and shipping), and pretty simple to wire up.
So here is the beast more or less finished. There is good reason that these germination chambers are also called “sweat boxes”. It is quite moist, and there is a lot of dripping. My design proved a little faulty in that all the water that dripped down the door ended up leaking through and onto the floor. A quick improvement for that was to use (again) a bit of tuck tape and make a little baffle to make all the drips go further into the box where they would run into the sink. We also tried to cover the water pan with metal sheeting to see if this would limit the sweating effect while still radiating heat into the box, but removed it because I felt like it was just going to use more power to heat the box.
Although we don’t have to add water to the pan that often to keep the level where it should be, a water line with a float valve would be good (for when someone forgets to refill it and the heater element is no longer submerged).
It’s not perfect but it works pretty well and it saves space and removes our worry over trays drying out pre-germ.
Here’s a re-cap in pictures of how it was built: