Pit Greenhouses or Walipinis. Depending on latitude, but despite above ground air temperatures (and wind chill), 6 to 8 feet down into the earth, temperatures remain fairly constant, between 50 and 60°F. Meaning your pit greenhouse will be much warmer than an above ground greenhouse in winter and that cool earth will keep temps bearable in the summer.
Growing lemons and oranges in Nebraska? Impossible, would be the first word most people would think of, but not Russell Finch. He bills himself as the largest citrus grower in all of Nebraska. Besides citrus he also grows pears, avocados, figs, roses, yucca, agave, hibiscus, and hundreds of other types of flowers, fruits, vegetables, trees and plants. His secret? A home-built “underground” greenhouse.