Growing Underground

London is a city with more space than the cities of the north and midlands have, but land is very expensive and the price of houses is so excessive that ordinary people cannot afford to buy. Any land is snapped up very quickly,so while there are a few urban farms in the city, they occupy a small fraction of the land. But the demand for food in a conurbation of ten million people is great, and most of it comes from outside. But there are enterprising people who grow either on roof tops or in cellars, and while there is no space in cellars or tunnels for animals, who should not be imprisoned thus, it is possible to grow certain vegetables beneath the ground if the conditions are made right. 

You have all seen pictures of London during the Blitz, with citizens crammed into tunnels where they slept on the ground while bombers pounded the city above. The bombers have gone, Germany is now a much-valued friend and ally, but the tunnels remained, dark and silent, almost forgotten, but not by everyone. Then along came two friends, Steven Dring and Richard Ballard, men with an ecological conscience and a yearning to use urban space to grow food for cities. Having looked above ground their fears were confirmed, there was no space for urban farming,but what about the tunnels, they wondered? It soon became clear that they would be permitted to rent the tunnels for growing, and so the enterprise,Growing Underground, began.

There are advantages and  disadvantages to underground farming, and to be exact what they are doing is more akin to market gardening than to traditional farming, for it resembles a market garden more than it does a farm. The two friends, however,are not ones to cavill over tight definitions. The lack of light is remedied by low cost, low intensity led lights. There is a water recycling system and there are fans to circulate air. This is essential as plants kept in still air can develop fungal diseases such as botrytis, which is always lethal to the plants that suffer it. On the other hand the lack of soil means that there are no weeds, and as one who has had to struggle with weeds on an allotment that is one sure advantage. The growers are also very near to their markets, which are restaurants and some high quality greengrocers in London, which cuts down their costs. The growing of vegetables in the cities is very ecologically beneficial, as it cuts down air miles and CO2 production, and they also make the most of otherwise unproductive urban space.

The farm specializes in herbs,  with about twenty varieties being grown. These include peashoots, red mustard, chives and coriander, among others. Clearly the hydroponic system cannot be suitable for all crops, and the tunnels, which had space for eight thousand people are now fully used up. But specializing in a crop for which there is a good market is advantageous as it enables the growers to develop their expertise. 

Hydroponics works on the principle that soil contains both active ingredients [the nutrients] and an inert growing medium, so any inert medium will suffice,  as long the nutrients are provided. In hydroponics there is an inert growing medium, which could be small pebbles or gravel composed of clay or artificial silicates. These are always non-toxic. The medium is kept in trays which are provided with nutrient enriched water. The nutrient content of the water is constantly refreshed by a computer based system which analyses the nutrient levels of the water and  replaces lost nutrients.In hydroponic systems the water use is minimized by recycling. 

Not all hydroponic systems use grow lights, which can be very intense. I saw this once when a house near my church was being used as a cannabis farm. One night the curtain fell down,  revealing a light of an intensity that I had not seen before.When I passed, the place was swarming with police officers. Growing Underground does not require grow lights of this intensity, for herbs require less light than cannabis does. Low intensity LED lighting is enough,though specialist lights for growing will be set to produce light of the frequency most suited to plant well being. 

In Growing Underground the herbs are grown in large trays, with the nutrient rich water being pumped through the base, while the plant roots reach down through the growing medium to the water below. 

Air temperature is controlled so that the room is kept warm but not too hot. In this way plants do not suffer from excessive transpiration. Both humidity and temperature are computer controlled so that the excessively humid conditions that cause fungal infections are prevented. The computerized system also allows for an airflow, yet another important defence against fungal infections. The room will also be maintained in a clean state to prevent its harbouring bugs that affect plants. 

There is no biological distinction between a mushroom and a toadstool, but the functional, culinary distinction is that mushrooms are fungi that you can eat, whereas toadstools are fungi that you cannot. Many mushrooms were grown in tunnels in France, and this practice gave rise to the mistaken belief that fungi grow in the dark. This error has been reinforced by the fact that field mushrooms  sometimes spring up overnight, in heavily manured fields. But mushrooms do not need much light,which is why some grow so happily on woodland floors. Some who farm oyster mushrooms  grow them in dark sheds,  and I have seen a film of a man who farms them in a small cave, over whose entrance is a wall and a door. Mushrooms will grow in low light, but they do not need total  darkness.

However,of critical importance is an airflow. Fungi are not plants. They have no chlorophyll, so they cannot photosynthesize, so they rely on the growing medium for nutrients. It is not well-known that fungi are neither animal nor plant,though they are closer to animals than to plants. They are air breathers,so they need a constant supply of air to provide them with oxygen,otherwise they remain small,brown, underdeveloped and inedible.You do not grow mushroom by hydroponic methods, for a watery growing medium does not work with them.  They do not require a completely dry medium, so it must be kept damp.When I grow oyster mushrooms I ensure that the growing medium is kept moist by spraying it regularly, and for those mushrooms that grow in a soil/compost medium the rule is that the medium must never dry out. 

There is scope for growing mushrooms underground,just as there is scope for herbs. However, the problem of the power supply for underground cultivation is a weak point, for electricity is expensive in the way that the free light from the sun is not. Moreover, while tunnels maintain a steady temperature, they are not warm, so they must be heated to a temperature optimal for plants, again using power. However, wind power and solar panels can go some way to resolving this problem. But minimizing power usage is an important economic factor in underground growing.