Tuesday, April 5, 2011

Our New Propagation Greenhouse

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.


  1. Heh..that's like my little green house...row tunnel..whatever)))Lee Valley? We love ours but I must say, yours is in better condition)).

    What a clever idea Owen..roof de-icing cables..wonderful! gives me all kinds of ideas..can't wait to see the tomatoes growing. Your Wentzells are growing great guns under lights as are all the tomato seeds we bought from you..all germinated.

  2. Yep, that's the same one! It had been sitting in the barn for a few seasons after a goring incident with the cow ripped up the plastic, but in the still greenhouse air my repair job seems to be holding together.

    It's working well so far... it's full of rapidly growing little tomatoes. It stayed warm even during that -8 night on Friday, It was actually -2 under the cover that night but it almost seems like the plants themselves absorb the bottom heat and don't get frosted.

  3. Hey Owen, This is a great idea. Did it work out well thru the whole season? Did the plants get too hot later in the season and did you have to take the extra plastic layer? How thick was the soil layer over the cables or did you put soil blocks on top of the cables or what? Just curious about the details... thanks, Ann

  4. Many farmers are use this techniques. and its is also good method and become it popular. soft and small plant do not adjust with sun heat and sun rays.

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