The polytunnels are a planet-friendly way to extend the UK season, allowing us to grow delicate salad veg year-round without artificial heat or light. And like everything we grow, it’s all 100% organic.
Ed Scott, a Riverford stalwart, oversees the polytunnels. Ed has been with us since 2003 – we don’t know where we’d be without his green fingers! Every year, he and his team trial loads of different varieties to find the sweetest tomatoes and the crispest cucumbers. They choose varieties recommended by trusted organic seed companies, looking at shape, colour, how happily they grow, shelf life – and above all, flavour.
“Many of these varieties, we’re probably the only people growing them in the UK except home growers,” says Ed.
Each year’s winning varieties are grown really slowly, in real soil, so that they develop the best natural taste.
“I do think growing in the soil makes a difference,” Ed says. “Most people are growing these veg fairly artificially, hydroponically in rock wool or in grow bags. In theory, you can make nutrient solutions which give the plant everything it needs to live – but you’re not going to give it anything it doesn’t need, because that’s a waste of money. But actually, what if other nutrients and minerals in the soil are what gives it the flavour?
“And a bit of stress is supposed to improve the flavour, so if the plants have everything they need being fed to them, that probably has an impact as well.”
On the other hand, doing it the natural way is “a bit of a headache”, says Ed cheerfully. Cucumbers are particularly fickle beasts: “When they’re happy, they’re amazing – but if you breathe hard on them, they die!”
It’s not just how veg is grown that makes a difference to flavour, but when they’re picked.
“One good thing about us is that we can pick tomatoes when they’re ripe, leaving them on the vine until the very last minute – because we have such a short supply chain,” Ed says. “Many growers pick earlier, because the tomatoes will keep ripening in transit. The thing is, once picked, they’ll still turn red – but they won’t get any sweeter.”
Being organic means never using artificial pesticides. So, our first line of defence against pests on the farm is biological control; that’s controlling pests by encouraging their natural enemies. Every summer, aphid-eating bugs – such as parasitic wasps and predatory wasps – are released into the tunnels to help keep our salads safe. Planting fennel flowers also helps to lure beneficial bugs inside, such as hoverflies, lacewings and ladybirds. Their larvae are all enthusiastic aphid eaters.
“The predatory wasps are particularly good,” says Ed, “Because they actually fly around the polytunnel hunting the aphids down!”
Native bumblebees are also introduced to pollinate the plants. The tunnels already thrive with insect life – and Ed has plans to make it even more welcoming for them:
“I plan to do more with permanent beetle banks, planting strips of grass and wildflowers down the polytunnels that stay there year-round,” he says. “We want to encourage beneficial insects to make their homes here and stay in between crops, rather than leaving at the end of each season when we clear all the plants out.”
Green verges and borders are planted outside the polytunnels, to feed any passing rabbits, and stop them from being tempted in to munch our crops. But some visitors to the tunnels are just too charming to resist: “A grass snake moved into one tunnel, because it’s so nice and warm, and a hare gave birth and raised her leverets in another. The team just let them be!” says Ed.
