Multilayered Seedling Greenhouse

This is a picture of the inside of our original seedling greenhouse. (I am in the process of doing a major renovation this winter.) I’m standing inside of what I refer to as my inner cover. The wooden structure you see on the ceiling is actually a greenhouse inside of another metal bowed hoop house. The boxed in area where you see all the seedlings I refer to as my inner cover cold frame. This large cold frame has insulated covers that I slide over the 2x’s that run across the top to help to hold in heat at night. Inside that cold frame I have around 1000 gallon jars that I have recycled from a bakery a friend of mine use to own. I put water with a teaspoon of red food dye in each jar to help collect heat from the sun during the day and release it at night. So why have I done all of this? Every layer, like a hoop house, that you put over your plants gives you approximately one and a half garden zones of protection. So I’m in a zone 5 most years. One layer takes me to zone 6.5. Two layers. A hoop house inside of another hoop house takes me to a zone 8. Now add my cold frame with the insulated covers and jars and I have achieved a level of protection against the cold that Haiti can’t touch. In fact the lowest temperature we have recorded on our farm was -44 below zero F. It was February. The day before was sunny. The jars heated up to about 70 degrees F. In the morning when I came down to open up the covers I started a fire in a wood stove under the second layer just to take the chill out of the air so I could take the covers off the third layer. When I opened it, the third layer was still 58 degrees F. That’s 102 degrees warmer than outside! My material cost to build that insulated cold frame was $500 at the time. I have used it for about a decade. If I were to try to use propane or firewood to achieve the same outcome it would cost me thousands of dollars a year to pull it off. This photo is from a past year. Hope this helps. God bless your day!

Thanks for sharing Craig. That is an impressive temperature effect!
I guess having lots of small jars makes them easy to reposition keeping the space multifunctional. Did you experiment with different colours in the water?

Nancy Reading wrote:Thanks for sharing Craig. That is an impressive temperature effect!
I guess having lots of small jars makes them easy to reposition keeping the space multifunctional. Did you experiment with different colours in the water?

Thank you Nancy. I am new here so I am not sure how to do everything yet.

Yes having the heat sink be 1000 gallon jars makes it very flexible. In fact I will take jars into the garden and put them around many of my cold sensitive plants. Here in Michigan the summer evenings will often get down in the fifties. That can be problematic for melon pollination and pepper fruit set. My pepper plants are loaded though because I put four jars around each plant, and they are bathed in warm air over night.

I chose red for the liquid color because research from several universities have shown that red light around tomatoes and strawberries can increase their yield by 25%. I am not claiming that the jars are for sure doing it for me, but I do specialize in heirloom tomatoes for an Italian Chef. My plants do respond well to the warmth at night. If I used a black liquid it would run about 8 degrees warmer, but during the day that could be too warm for some plants.

I love the fact the those jars are all recycled. I have been using them for over a decade.

Craig Schaaf wrote:I will take jars into the garden and put them around many of my cold sensitive plants. Here in Michigan the summer evenings will often get down in the fifties. That can be problematic for melon pollination and pepper fruit set. My pepper plants are loaded though because I put four jars around each plant, and they are bathed in warm air over night.

I hadn't thought of that idea, but it makes a lot of sense!

My plants do respond well to the warmth at night. If I used a black liquid it would run about 8 degrees warmer, but during the day that could be too warm for some plants.

Hmm, yes dragging out my school day physics - matt black absorbs more light radiation than other colours so I guess it would get hotter. Great if all you wanted to do was increase the temperature though - I wonder how that might work in my new tunnel? I'll have to remember to make some experiments.