Extend your growing season into the cold by building your own geodesic dome

They may look like UFOs have landed in your backyard — or a miniature version of Walt Disney World’s Spaceship Earth attraction ended up there — but geodesic dome greenhouses can be hardy, weather-resistant ways to extend your gardening seasons when the Maine temperatures get cold.

And as any number of do-it-yourself videos available online indicate, they’re relatively inexpensive to make — with some experts saying the costs for materials can be as low as $200 or $300 for a couple hundred square feet of sheltered gardening space.

Simply put, the dome frames are made up of interconnected triangles which, when assembled correctly, make a skeletal hemisphere of sorts.

Those triangles can be built with sticks of wood, PVC piping or, for those with welding experience and the materials, steel.

One group used PVC piping for its 20-foot geodome and reported the project can be completed within a day’s time — click here for that account.

Here’s a link to a post by another group who used metal bars, featuring a video of how to approach the project using wood.

Geodesic domes are strong options deeper into the fall or earlier in the spring in a cold state like Maine because they optimally absorb sunlight no matter in the sky the sun is, and because they don’t give sharp seasonal winds or precipitation anything to grab onto.

But how much can they extend your gardening season?

The website NorthernHomestead.com reports that there are winters too harsh for even the most resilient unplugged greenhouses, but that growers can begin with peas and greens “as early as March” in a climate that still sees frost deep into May.

According to NorthernHomestead, the type of covering you use in building your geodome will also determine how warm it will stay inside, with options ranging from thin plastic to polycarbonate panels to specially developed clear insulation.

Other additions to the plan, like digging down and placing a frost skirt around the structure’s perimeter or using frost blankets over the plants themselves, can also add weeks to the geodome’s gardening season.

For another level of complexity, you can add a water tank as a temperature-regulating thermal mass — like a self-sustaining swimming pool for small fish, bacteria and aquatic plants — or add electric heating and fans.

But then you’re beginning to drift outside the $200 to $300, do-it-yourself-in-a-few-days project we started with.