This is an amazing story recommended by Jim, one of our long time readers and supporters. So many things such as fruit walls are being forgotten due to the prevalence of relatively affordable energy.
“We are being told to eat local and seasonal food, either because other crops have been transported over long distances, or because they are grown in energy-intensive greenhouses. But it wasn’t always like that. From the sixteenth to the twentieth century, urban farmers grew Mediterranean fruits and vegetables as far north as England and the Netherlands, using only renewable energy.
These crops were grown surrounded by massive “fruit walls”, which stored the heat from the sun and released it at night, creating a microclimate that could increase the temperature by more than 10°C (18°F).
In 1561, Swiss botanist Conrad Gessner described the effect of sun-heated walls on the ripening of figs and currants, which mature faster than when they are planted further from the wall. 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.
The fruit wall reflects sunlight during the day, improving growing conditions. It also absorbs solar heat, which is slowly released during the night, preventing frost damage. Consequently, a warmer microclimate is created on the southern side of the wall for 24 hours per day. Fruit walls also protect crops from cold, northern winds.”
More at the source: Low Tech Magazine