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How far can vertical farming go?

Vertical farming promises a future in which our food is grown in pockets of spaces in our cities and beneath our feet. But how far can it really go?

When the Pasona Urban Farm opened in the nine-storey office of a Japanese recruitment company in 2010, it promised a future in which food was grown within feet of the people who would eat it.

Tomatoes hung down from meeting-room light fittings, a rice paddy filled a large conference space, and mushrooms grew in drawers hidden discreetly under benches. The office looked more like a museum of farming than a place of work.

While the modern concept of vertical farming – growing food in trays or pipes stacked on top of one another like a giant plant lasagne – dates from around the 1990s, it could be argued that farmers have sought ways to grow more in less space and with less soil for centuries.

Step-over fruit trees – usually apple and pear trees – are grown as low as 1ft (30cm) off the ground and spread laterally to fill thin strips of space in allotments and orchards. The step-over technique is based on espalier training, which might date back to Ancient Roman grape cultivation.

What would a world where all our food is grown in such as way look like?

Vertical farming in the modern sense is now spreading rapidly. One example is the vertically farmed strawberry brand Oishii, based in New Jersey. In 2021, a punnet of its coveted Japanese Omakase strawberries retailed for $50 (£44) in a high-end New York supermarket.

One example is the vertically farmed strawberry brand Oishii, based in New Jersey. In 2021, a punnet of its coveted Japanese Omakase strawberries retailed for $50 (£44) in a high-end New York supermarket. For some, this was evidence that with time vertical farming could rival and ultimately exceed traditional farming for quality.

So what exactly is vertical farming?

There is no strict definition of what a vertical farm is, but they typically consist of shallow trays stacked within a building, lit with LED lighting at each level. Many vertical farms have no windows and some are even built underground.

These kinds of farms must supply everything – water, nutrients, sunlight and possibly pollinators and pest control too. Others might be built in massive greenhouses – making the most of the Sun's light and heat, but still controlling other inputs like water.

While sometimes soil is used, increasingly vertical farms use hydroponic or aeroponic systems, where water (for hydroponics) or water vapour (for aeroponics) infused with nutrients is circulated directly around the roots of the plant.

"The water efficiency and nutrient efficiency is really quite high in hydroponics and aeroponics because the roots are able to get those nutrients and water in a lot quicker," says Laura Vickers, a plant biologist and head of the Urban Farming Group at Harper Adams University in the UK. "There's no organic matter, there's nothing else for the plant to compete with or to extract the water from."

This means using vertical farms can considerably reduce both the water and fertilisers needed to grow food. Meanwhile, the closed-off, controlled environment of vertical farms can help to stop pests getting in – in turn possibly reducing the need for pesticides.

The technology can also allow crops to grow in locations where conventional farming is not possible. Astronauts on the International Space Station, for example, are growing their own food in soilless systems under LED lights – with cabbage, mizuna mustard, lettuce and kale among the crops on the menu.

A meta-analysis of urban farming in a variety of settings across 53 countries found lettuces, kale and broccoli were particularly suited to vertical farms. Crops like spinach can be grown from seed to harvest in 30 days, meaning a vertical farmer could have 12 harvests from the same tray each year. What's more, if the farmer were to stagger planting their crop from one row of trays to the next, they could have an almost continuous supply of food all year round from their farm – something a traditional farmer can only dream of.


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