Aah, sure does eating too much potatoes lead to a dark philosophy!

Working in a garden might be beneficial not only for the mental sense of "being rooted". There are scientifical studies suggesting that a common soil bacteria acts as an antidepressant. Or, maybe we'd better say that the philosohpical idea of "being rooted" is partly mediated by a biological bacteria - I mean, there is a meaningful exchange between human body and the surroundings. Just like we need food and water to stay alive, it might be that we need exposure to brute nature to stay healthy.

http://www.medicalnewstoday.com/articles/66840.php