Tips for icebergs: how tech is transforming lettuce growing
19 December 2019
What do we want? Lettuce. When do we want it? All the time, apparently. Lettuce is historically overproduced to ensure a constant supply, but suppliers are working out new ways to cut waste. Duncan Jefferies meets the modern lettuce grower.
“Lettuce is like conversation; it must be fresh and crisp, so sparkling that you scarcely notice the bitter in it.” So wrote the American essayist and novelist Charles Dudley Warner, whose main claim to fame is another bon mot that’s often mistakenly attributed to his friend, Mark Twain: “Everybody complains about the weather, but nobody does anything about it.”
Warner probably didn’t realise how closely the subjects of these quotes are linked: lettuce, like national character, is highly influenced by the weather. Cold snaps can significantly slow its growth. But it’s also very sensitive to high temperatures, and may “bolt” (flower and turn bitter) if it gets too hot.
Sensitivity to the weather is also something the lettuce shares with many of its British fans. No food fad has quite dislodged our fondness for the cool, crunchy iceberg – particularly when the sun is shining. Barbecue-worthy weather sees the lettuce heads flying off the shelves faster than you can say, “the sausages are burnt”. In fact, during the June 2018 heatwave, the UK chomped its way through almost 18m in a single week.
As lettuces can’t be frozen or stored for long periods of time, producers have historically grown more than they think they’ll need, to ensure supermarkets don’t run out when demand spikes. Ideally anything left over is sold on the wholesale market. However, an oversupply of lettuces can cause a price collapse – at which point it no longer makes financial sense for farmers to harvest any excess left in the fields. Instead, these extra lettuces were, historically, ploughed back into the land.
More accurate forecasting by growers was cited as one of the best ways to stop this waste from occurring – an issue that Tesco and its lettuce supplier of more than 40 years, G’s, have tried to address together.
Working with mathematicians at the Smith Institute, G’s has developed a sophisticated growing model called IceCam (Iceberg crop adaptive model) to help predict spikes and troughs of crop availability, and more accurately match supply with demand. Having access to such information also improves overall freshness.
Data on temperature and humidity within specific microclimates, as well as historical weather data and forecasts, is fed into the IceCam algorithm. It then predicts the probability of undersupply or oversupply, and creates an optimal plan for sowing, planting and harvesting. If necessary, G’s can then change its sowing and planting schedule to prevent any shortfall in supply.
“It helps us to grow the correct volume [of lettuces] at the correct time, and also react to sales trends and weather patterns,” says Rob Parker, leafy salads crop manager at G’s.
Previously, G’s was using basic historical data to forecast when its lettuces would be ready to harvest. Parker says the decision to invest in a more high-tech system was driven by a desire to reduce the amount of waste that occurs in the field. “We could see that we could potentially make savings in the supply chain – a reduction in waste, better utilisation of land and resources – by having a more detailed understanding of our crop growth and crop cycles,” he says.
Working with Tesco has been key for getting the most out of the IceCam. Supermarket promotions, for instance, can help to soak up any excess lettuces – Tesco running special offers after bumper crops, say – and the IceCam offers a useful time advantage during the planning stage.
“It can tell us two or three weeks in advance when we can expect to have surplus supply,” says Parker. “That gives us time to work with Tesco to line up a promotion or initiative to try and move that volume, because nobody wants food waste anywhere within the supply chain.”
Indeed, this helps Tesco meet its own food waste target: that no food fit for human consumption goes to waste, across all of its UK operations.
G’s is now combining IceCam with aerial survey data collected by drones, allowing the firm to monitor the growth stages of its iceberg lettuces and assess whether they are matching expectations. Parker says this hones the IceCam’s algorithm.
“We can say ‘the model expects the lettuce to be this size, but our data suggests it’s in front or behind,” he says.
“We can then react to that to ensure that the lettuce is still ready on the day it’s intended to be ready, and that it hits the shelf on the day we want it to hit the shelf.”
In other words, the art of growing lettuces, like the art of conversation, is all about asking the right questions and responding quickly to the answers you receive – even when they’re not quite what you were expecting.
Waste not want not
Tesco has committed to cutting food waste: setting an ambitious (but achievable) goal that no food safe to eat should go to waste across its entire UK retail operations.
That means working with producers such as G’s to create innovative solutions to food waste, for example saving fresh food with minor natural imperfections (like wonky veg) for its Perfectly Imperfect range – or turning really wonky (but still delicious) veg into ready meals. Or donating safe, surplus food to local charities and community groups. All this means the supermarket is already 80% of the way to ensuring that no good food goes to waste.
For more stories on how Tesco is working to improve how we get our food, visit http://tescoplc.com/sustainability