By building tubing which could serve as water reserves, the electronics could heat the soil without coming in direct contact with any liquid. Using a fairly large enclosure, he was able to build an entire soil bed that doesn't rest or touch the hard drive or any other component. (And don't worry, he didn't use his primary PC for this project.) Once it was built, the other main challenge was getting the temperature right. Mike says: "Using the fans to control the case temperature allowed me to vary the temperature inside the case from a low of 75°F (24°C) to a high of 91°F (33°C). In order to achieve the desired increase in soil temperature, I had to run the case temperature toward the higher end of the scale."
It's certainly not a hack for those without a green thumb or computer building savvy, but perhaps it may inspire smaller scale tech+plant growing endeavors. In case you're curious about the plant: it's wheat grass, which needs plenty of heat to grow and took well to Mike's new planter. You can see the full explanation of his project on his blog, Total Geekdom. (Image: Total Geekdom)