I had a dream once. – I am standing in a vast green summer field looking down into the earth. The ground is a large glass roof in the shape of a cross. I can see tropical plants and seedlings flourish in the warm, light flooded space beneath. There is a sacredness to the space that is breathtaking. – I woke up and remembered both the beauty and impossibility of the vivid dream. Plants growing happily underneath the earth? Can’t be.
I met my farmer friend Verena a few weeks later and my dream came up during a conversation. She said, “Yeah, it’s called an earth-bermed greenhouse. You can build such a thing and it’s been done before.” Really? Well then, I thought, let’s make a dream come true.
It took me a while to find the person who was willing to embark on the adventure with me. My friend Jesse, a natural builder who is always on the lookout for new territories to explore, gave in to the calling.
What was supposed to take a couple of months at the most turned into a year long journey, as he ended up not only building a practical and functioning earth-sheltered greenhouse, but a piece of green architecture that feels and looks like the sacred space I dreamed about three years earlier.
We used the basic building plans from Mike Oehler’s book The Earth Sheltered Greenhouse for the layout and material list.
An earth-bermed greenhouse is best build into an already existing South facing hill with full sun exposure. We started clearing shrubs and fallen trees from an area close to the house matching these conditions and decided on a 16×16 foot growing space. Oehlers’s plans include digging out a 3-4 foot deep “cold sink “ at the South side of the greenhouse. A space that is designed to allow cold air to settle into at night, rather than hovering over your tender seedling that are growing in the work space.
The soil in our area has a lot of clay and does not drain water well. We added French drains around the whole outside perimeter to redirect the water flow around the structure. French drains are trenches with perforated pipes that are wrapped in landscaping fabric. The trench then gets filled up with crushed #4 stone and covered with top soil.
Next we started digging the 3 foot deep post holes. Even with the drainage system in place, the holes immediately filled with water and we decided to add PVC socks to the 6×6 pine posts to make sure they would not be exposed to moisture in the ground, preventing them from rotting. After setting the posts the holes where back filled with cement.