Fruit walls in the 1800s.Gessner’s observation led to the emergence of the “fruit wall” in Northwestern Europe. By planting fruit trees close to a specially built wall with high thermal mass and southern exposure, a microclimate is created that allows the cultivation of Mediterranean fruits in temperate climates, such as those of Northern France, England, Belgium and the Netherlands
I like that, until the age of the water-pipe-heated wall, these are just walls. Nothing special had to be done with them; you just had to plant fruit next to them. Via
Eric.