Underground greenhouses

There are a few interesting ideas about greenhouses, seen as places where to grow food also in very extreme weather conditions. In this case, it's about doing it underground, using the thermal mass of the Earth to keep the inside at the desired temperature.
To tell the truth I don't really like the use of plastic materials but I definitely consider the goal as one of the highest priority of every human settlement.

"The Walipini utilizes nature’s resources to provide a warm, stable, well-lit environment for year-round vegetable production. Locating the growing area 6’- 8’ underground and capturing and storing daytime solar radiation are the most important principles in building a successful Walipini." [1]

What to say? The project looks very successful as it started and very well promising.
I am just wondering if a system of living shades (trenches with vines) and a partial green roof wouldn't do enough... anyhow attaching a greenhouse to a house it's a pretty straight forward idea but in this case it would be like attaching it... to the basement!

Keeping it mind, just in case.