Yes it is, as these things always are, temperatures can drop to 5 degrees in the cool season at this farm if I understood properly, and as with all these factory farms, the reality is, grow plants emerged for no algae problems and with CO2 levels of at least 400 ppm plants with good nutrition (no soil used, not even fancy pelleted soil) flourish.
I was very surprised about the 5 degrees. I wouldn't have thought that was possible.
Yes so was I but then they were under cover, pelargoniums can cope with 5 degrees - I bring mine in during the last week of October though by then they are often a bit damaged but pick up with a feed and bit of heat in the house, but they are from the subtropics - South Africa originally I think.
I think it works because it is only for very limited periods. A few years ago <"I stayed in Rotorua">, during the New Zealand winter, and it was actually frosty on quite a few nights, but 13 - 14oC during the day. There is natural geothermal activity, so the earth would have stayed warmer, a bit like the water in the video.
