Earth-sheltered cold frames

I have a piece of plexiglass (about 32”x48”) and would like to use it to make a cold/warm frame, mostly for starting seeds of perennials and some annuals, and so I’ve been thinking about how it could be done in a more resourceful or creative manner.

It surprises me that I have never heard mention of making an earth sheltered cold frame, but if there are earth sheltered greenhouses, then why not? Our soils here in Vermont can get very soggy in the cold season, so appropriate drainage would need to be arranged. Maybe rubble drains on either side of the growing area? And then, one would need to retain the earth by way of some stone or stone-like material. I would love to use stone for that purpose considering how much is around, but hope it doesn’t attract too much rodents. There is also an easy source of gravel from the river.

Another thought is to make a compost windrow that goes around three sides, providing insulation and heat. This might be a little easier for drainage, and provide some additional CO2.

I’m not very experienced in building of any sort, let alone natural, so hope to learn something through this process and also to ignite some of your imaginations. And it would be interesting to hear whether anyone else has been doing something similar or has some advice or initial thoughts.

I feel your idea would be very effective.

And this sounds like you would be solving two problem at the same time.

This reminds me of creating a "micro-climate".

https://permies.com/t/138107/Permaculture-Ideal-Microclimate-Aleksandar-Stevanovic

Does this help
https://www.gardenandgreenhouse.net/articles/greenhouse-articles/the-walipini-greenhouse/

A beginning has begun for the earthen kind: a trench in a light, well-drained south-facing hillside covered with large sticks and then with the plexiglass sheet. The middle one is a buckthorn trunk to be debarked some time soon, the outer two are something half rotten I found in the river and took out some time ago. Essentially, a beginning for the sake of a beginning, extremely cheap and not likely to work very well, absolutely not rodent-proof, but improvements can come later. If it fills up with water, then I can make a ditch above it and we will see if that works.

As it comes together, I can imagine—rather than growing right in the ground as I had imagined at first, now I see pots and trays and jars full of seeds stratifying. And in spring and summer, the consistent humidity and more moderate temperature could be a blessing for starting seeds for the summer and fall gardens in a climate where late spring especially can be dry, hot, and inhospitable for seeds and seedlings.

Still to be done would be evening out the floor, or adding enough compost to make an acceptable growing surface, as well as probably adding some more logs to raise up the window so that it catches more light and so that snow can slide off more easily. It would be small for growing anything, but the idea of even a few cold hardy greens while it isn’t being used for seed starting is welcome.

John C Daley wrote: Does this help
https://www.gardenandgreenhouse.net/articles/greenhouse-articles/the-walipini-greenhouse/

Thank you for the link—that is indeed quite useful, and good to hear that people have been doing the same in my region with success. Maybe I will have to make a cold sink in the future, or maybe it will be sufficient to elevate the plants. Another option may be to add some composting materials and keep that underneath the plants.

The project is so far going well. I don’t remember observing any frost or freezing going on inside the trench, and if it has, then it hasn’t been for any long time period. Neither has it flooded, contrary to my fears. I plan to continue and make more of the same kind, perhaps making some into hot beds.

Our minds go to all sorts of worst-case scenarios. Left to their own devices, they tend to plan out and worry about and bombproof our designs. But I don’t see any bombs around… fortunately…

[quote=Maieshe Ljin]It surprises me that I have never heard mention of making an earth sheltered cold frame[/quote]

maybe everybody's too busy going to the grocery and big box stores. thanks for sharing a good idea. i'm wondering if it would become the chipmunk sauna around here.

Overall it worked well. Everything survived, and I recommend it for anyone wanting to keep semi-hardy plants alive (it did get frosty in January and February) but it extended the season of the potted plants, and the cabbage and garden rue survived as evergreens, the leaves not dying back. In spring, I sadly ended up scorching some chrysanthemums I put there because it was so hot.

The ideal angle of glass in my latitude is roughly 23+43=66 degrees, which should catch the most sun at the winter solstice. So my setup is far from ideal currently. But it has worked. If you want to keep some semi-hardy plants over the winter and have a spare pane of glass then it's so easy to make. A few hours of digging, three sticks, and a little platform to keep the pots off the ground.

I've seen and used a method somewhat like yours before, with fair to good results.  It was from an old Rodale Press book (late 1970's) using bales of old straw as a surround and covered with an old window sash.

I did the same thing, only using several clear view storm doors, it did well with keeping us supplied with fresh greens most of the winter.  Also tried the same in the green bean patch, hoping to extend the season a little longer.  That kinda worked, for a short while, the beans made it well into November, maybe into early December.  I think that the beans just couldn't handle the extended cold days and frosts.

You have to try, to learn!

Peace