I'm very excited about the new heated propagation bed that I rigged together last week. It's a bottom-heated mini-greenhouse inside our big greenhouse, I'm hoping to use it to produce lots of tomato seedlings for the local markets later this Spring. A few days ago I planted the last of the seeds in it... we're up to 30 varieties of tomatoes to be available as starts if all goes well!
Here's how we made it:
-We laid down 1" styrofoam sheets from Home Hardware (duct-taped together in the shot) to act as insulation and to prevent the heat from dissipating into the ground. Each 4'x8' sheet cost around $10.
-Next we covered the foam with a layer of earth...
... and laid down the heating cables. They're just roof de-icing cables from the hardware store, this is an 80' length and cost about $60.
-Finally, we covered up the cables with another layer of soil, plugged in the cable and voila! Finished propagation bed! The earth retains the heat from the cables and distributes it fairly evenly. Once the cover is back on the mini-greenhouse it will stay above freezing even on cold nights when the kale in the foreground gets frosted. We also have small air heater (visible on the far right) that I might put under the cover and use if it gets below, say, -5 while the plants are up and vulnerable.
So the whole project took an afternoon to assemble and cost about $80 using new supplies, not bad considering how many hundred of plants it'll grow! The mini-greenhouse itself was an old one we had kicking around in the barn, it wouldn't be hard to rig up something similar using perhaps PVC pipes or whatever you have handy.
