Nebraska Retiree Grows Citrus with an Earth-Heated Greenhouse

HN commenters bring it up in geothermal, greenhouse and vertical farming threads as a low-tech example of growing citrus in a cold climate.

Kirsten Dirksen visits retired mailman Russ Finch in Alliance, Nebraska, who grows oranges, figs and pomegranates in a backyard greenhouse without paying for heat. The greenhouse uses the stable temperature of the earth, with underground earth tubes, to heat and cool itself.