Year-Round Produce: Wyoming Gardener Outsmarts Winter With Underground Greenhouse

Two-year-old Huxton’s favorite thing to do at his grandma Sara Ross’ house is something not that typical for Wyoming winters.

He loves to trudge past the snow and on into a toasty warm underground garden, where he hand-picks a few fresh carrots from the ground for a little afternoon snack.

It doesn’t matter that where grandma lives in Daniel, Wyoming, is in the deep freeze of winter. It doesn’t matter because Ross has figured out a way to outsmart Mother Nature.

Her little trick is something called a walipini, which translates to “warm place.” A walipini is a greenhouse pit dug down into the earth so that it stays insulated and above freezing all winter long. That means when other Wyoming green thumbs are starting to plan their spring and summer gardens, Ross is picking and growing produce.

“Right now, I’ve got some romaine lettuce and two different types of spinach growing in there,” Ross said. “And the peas — regular table peas and some sugar snap peas — have just kind of poked their little heads up.”

There are several herbs still growing in the underground greenhouse, as well as blackberry plants, leftover from the summer.

“We just started some beans,” Ross said. “And there are some just random little flowers that I held over from last year, because I wanted to keep them going.”

The carrots that young Huxton craves, meanwhile, are on the shady side of the walipini, which Ross said makes excellent storage for root vegetables all through the winter.

“Carrots are just happy to stay in the ground as long as they’re not too moist and not too dry,” Ross said. “So, we just go down there and pull those out whenever we want some.”

With March having just started, Ross already has tomatoes and pepper transplants growing in her home, which she’ll be able to transfer to the walipini long before they could normally be transplanted outdoors in Wyoming.

“Once they’re planted down there, they do really well,” Ross said. “I had tomatoes from last spring through December, and then I just decided to pull them out because they were starting to look a little sad. But they were tall, you know, they were 5-foot tomatoes.”

Who Started Walipinis

Walipinis arose in the mountainous regions of South America, which also has a pretty short growing season, and they got an in-depth look in 2002 from the Benson Institute in La Paz, Bolivia.

The idea behind them is relatively simple.

The Earth’s center is a molten core of magma, which helps keep it warm, an effect that’s noticeable starting at about 4 feet below the surface.

Large amounts of dirt, meanwhile, act like a giant heat sink that evens out temperatures — warmer in winter, cooler in summer — an effect commonly seen in caves.

To make her walipini, Ross dug out a 14-by-20-foot area 7 feet deep, then covered the pit with a slanted, south-facing greenhouse roof so that sun can still shine in on the plants inside.

A small wood stove heats the space at night, while during the day, the sun takes care of keeping things nice and warm for the plants.

A Just Do It Mentality

Ross moved to Wyoming from Missouri, where she enjoyed a generous, 170-day growing window without any real need for season extension.

When she moved to Daniel, she had a bit of a garden culture shock realizing that she would have just 57 growing days to work with.

“I was kind of like, ‘Oh my goodness, I can’t grow anything!’” Ross said.

First, she tried a greenhouse made from a recycled trampoline frame, but that didn’t provide enough season extension for all of the things she wants to grow.

Remembering an old Pinterest post for something called a “walipini,” Ross thought that might just be her answer.

She didn’t find too many instructions online about how to actually build one, but she didn’t let that stop her. She decided to take the Nike motto to heart — “just do it.”

Dig To The Boulder

She and her husband were actually going for a pit 10 feet deep.

“But we hit a boulder that was like the size of a Volkswagen Bug,” Ross said. “So, we were like, ‘OK, I guess that’s where we stop.’”

Next, they visited a local sawmill and bought one trailer-load of slab wood for a mere $35. That made shoring up the walls fairly inexpensive.

“We also have a sawmill here at our house as well, because we dabble in a little bit of everything,” Ross said. “So, like the dimensional lumber for the roof, the posts that stand in the middle for structural support are just little pines from out in the forest here.”

The first roof the couple tried was made of corrugated plastic, which proved too brittle in the cold and snow.

“We have a broom with an extended handle to sweep off the snow,” Ross said. “And if you got the broom on there just a little too hard it would crack the panels.”

Ross soon realized her roof wasn’t slanted enough for the sunlight to shine fully in, so this past fall she redesigned things. The roof is steeper, about 3 feet off the ground at the back end, then angling down to ground level on the front.

“That also helps keep water and snow and everything else off, too,” Ross said.

And this time she used double-walled poly panels — similar to what most greenhouses use — for a clear roof that lets glorious sun shine into her walipini.

Some Heat Required

Although insulated by the ground, the walipini still gets cold at night once the sun quits shining, so Ross has a small wood stove inside. It provides auxiliary heat on cloudy gray days when the sun isn’t really shining, as well as at night.

“The stove does not burn all night,” Ross said. “We figure the stove probably burns until about 3 a.m. in the morning.”

Ross has placed rocks around the small stove, which catch and hold the heat a bit longer once the fire has gone out.

“This morning when I got up with my grandbaby at 5:30 a.m., it was 59 in the walipini, so it does pretty well,” Ross said. “On cloudy days, we might start a fire midday just to keep up the temperature, but usually we don’t go down there until about 8:30, 9 p.m., so right before bedtime.”

Ross believes if they’d been able to dig out the Walipini pit to 10 feet, they wouldn’t need as much auxiliary heat.

“The deeper you go the warmer you’ll stay, because you’re getting further into the ground,” she said, adding the walpini still does pretty well at 7 feet deep.

“During the day, with the sun, I mean we could be negative temperatures outside, but when the sun is shining it’s 60, 65 down there,” Ross said. “On really warm days, it can get up to 75 degrees.”

In summer, the submerged greenhouse can get a little too warm with the sun shining in, but Ross has a solution for that too. She’s hooked up an exhaust fan to a thermostatically controlled outlet.

“If it gets above 77 down here in the summer, the fan will kick in and pull out all the hot air until it gets down to about 72.”

The walipini has almost made winter her favorite gardening season, and she’s already plotting out all the things she’ll grow that often don’t do so well in Wyoming — spaghetti squash, long-season peppers and, of course, everyone’s favorite, tomatoes until December.

“I have a camping chair down there, and I like to sit down there some days and just chill,” she said. “It’s also been fun to share this with other people. Hopefully, it’ll give people some gumption to try this on their own.”

Renee Jean can be reached at: Renee@CowboyStateDaily.com