What is an Underground Greenhouse

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An Underground greenhouse, also known as a Walipini or pit greenhouse, is a greenhouse that is dug into the ground. These greenhouses take advantage of the natural insulation and protection that comes from the soil. They are a much more earth-friendly and efficient option than standard greenhouses. Plus, if you’re careful in how you acquire your building materials, you can build an underground greenhouse for very little money when compared to a more traditional option.

Why Choose an Underground Greenhouse

Almost any piece of land can support an underground greenhouse and keep you happily in fresh vegetables all winter long. Underground greenhouses are less affected by varying climate changes throughout the season. This is because the dirt provides some natural insulation from both the hot and cold. They’re easy to use and have been used by people for thousands of years. In fact, a backyard root cellar is little more than an underground greenhouse repurposed for growing instead of storage.

So what is a Walipini?

Walipini’s, or underground greenhouses are nothing more than holes in the ground. They are about eight feet deep and aligned so that the sun comes through the roof on the southern side. The dirt to the northern side provides insulation and warmth or cooling depending on the time of year. Constructing this kind of greenhouse is super easy and can even double as a root cellar. You just have to be clever and careful in how you set up ventilation and walkways.

I have been considering and leaning towards a walipini for our garden on the new homestead. I love the ability to grow vegetables all year, without having to invest a bunch of money in a greenhouse. The idea of a lone, glass sided greenhouse against the hail out there just makes me sad. But with a pit greenhouse, the biggest consideration is the orientation to the sun and how to roof it. It’s pretty much a no-brainer for us!

Building A Pit Greenhouse on Your Homestead

Building an underground greenhouse requires some basic knowledge of your land. First, you have to consider what kind of soil you have and whether you will need to shore up your dirt walls with bricks or wood. Secondly, you want to spend some time getting to know the location where you plan to build your greenhouse and the soil you’ll be building it in. At the very least you want to know:

• Soil Composition
• Depth of the Water Table
• Frost Line
• Where South-Facing Is

Your soil composition will determine how much and what kind of drainage you need. You will still have to water your vegetables in your pit greenhouse. You want to be sure that there is drainage in place and even better if you can create a water reclamation system.

The depth of your water table is also crucially important, as is the frost line. Your walipini should be 6-8 feet deep but also at least 5 feet above the water line to prevent flooding concerns. In addition, temperatures in your greenhouse will be more stable if you can begin closer to the frost line rather than at the surface level. Some people have countered this issue by creating a cool-air sink that allows cold is to circulate outside the growing space where it can then be heated by the lower soil and rise back up into the garden area.

Lastly, knowing which direction is south is absolutely a must for any greenhouse! Greenhouses do best when they are southern facing because then they receive the greatest exposure to sunlight all year round. This allows them to generate more heat and encourage growth. If you are living in a place with a very short growing season, this will also help to reduce the amount of money that will need to be spent powering grow lights.

Costs of Building an Underground Greenhouse

While it can be challenging, it does not have to be terribly expensive to build a pit greenhouse. Cost depends entirely on the availability of materials in your area and your willingness to get your hands dirty. Renting tools for excavation and buying new lumber or concrete bricks to shore up your walls will naturally cost more than digging out your greenhouse yourself with a shovel and finding materials for free or for cheap online.