US: Vertical farms can do leafy greens without problems

Matt Barnard is the CEO of Plenty, the agtech start-up he founded in 2014 after a career in tech and finance. The San Francisco-based firm grows crops not in fields or polytunnels but indoors on six-metre-high vertical poles. Their roots are fed by a slow trickle of nutrient-rich water. There's no soil and no pesticides - as there are no pests and there's no sun; light is provided by LEDs.

The idea is that indoor farms like this can be built close to population centres, cutting the length of the supply-chain and leaving farmers to concentrate on growing crops for flavour rather than durability. City-centre hydroponic farms aren't a new idea, but Plenty is making progress on that toughest of products: tasty peaches.

Barnard: "Right now, produce often has to travel 4,500 kms from the farm to consumer, which is why so many farms grow iceberg lettuce, which tastes of nothing. Our salads are spicy and citrusy and sweet at the same time. People are amazed they can eat it without salad dressing."

Wired.co.uk writes how, apart from kale and that tasty salad, Plenty currently supplies strawberries, carrots, tomatoes and watermelon to a number of local retailers from a single farm in San Francisco. But it is trialling about 400 crop varieties at its test centre in Wyoming and has plans to expand the range ‘quarter by quarter’.

"We can pretty much grow everything," he says. "The problem is cost. The challenge is to get your produce down from $80 per kilogram to $2. At the moment, for example, we still have an expensive peach".

His strategy for reducing costs (and improving taste) is to add data and machine learning to the traditional hydroponic mix. Arrays of infrared sensors monitor how the crops are growing and feed that information back into algorithms that adjust light, heat and water flow accordingly.