Gardeners see which crop combinations work best

_{Text: Tefke van Dijk}

Thousands of gardeners across the Netherlands with vegetable patches have once again been busy this spring sowing, measuring and weighing crops such as broad beans and beetroot as part of the MoestuinMix project. They record data on seedling emergence, plant height, flowering period and yield. With over 2,300 gardeners taking part, this third edition has broken the records. ‘We were surprised by our own success,’ says project leader Yvonne Florissen.

The project aims to find out what combinations of crops work best. ‘This year, everyone taking part will test the combination of broad beans and beetroot, as well as broad beans with a crop of their choice. These two pairs are then compared to see how the beans do when grown alongside different plants.’ Keener gardeners can also list the insects they see – pollinators such as bees and hoverflies, as well as pests such as aphids. They also record diseases, fungal infections and growth issues in general. Taken together, all this data will show which combinations work well.

Florissen and her colleague Zoë Delamore are running this citizen science project from the Laboratory of Entomology. Each vegetable gardener receives the seeds plus a comprehensive guide and instructions on how to record all the measurements. In return, they share their data. Ultimately, all these pieces of information come together to create a comprehensive picture that helps researchers understand how crops can enhance each other’s performance.

Pest control

MoestuinMix is part of the five-year CropMix research programme, which is studying how crop diversity can help make agriculture more sustainable. The programme focuses on ecological growing methods, biodiversity and natural pest control – all aspects that have largely disappeared from farming after years of monocultures. ‘CropMix has about 70 researchers, 35 consortium partners and a network of around 25 farmers, all practising some form of strip cropping,’ explains Florissen. ‘But we wanted to involve the general public too, and people with allotments or vegetable gardens are ideal participants.’

Unlike modern arable farmers, people with vegetable gardens naturally work with a diverse range of crops. They rotate and combine crops and keep an eye out for pests, often based on experience handed down over the generations. ‘Allotment holders have a lot of local lore,’ says Delamore. ‘For instance, people have been saying for years that onions and carrots go well together. But is that really the case? And why?’

The first two years of the project have already yielded some striking insights. For example, broad beans grow better next to chard than beetroot, despite the close relationship between those two crops. ‘That raises questions. Why is one crop a better neighbour than another? We also see that crop combinations aren’t equally good in terms of all aspects. A particular combination may work well against pests, for instance, but attract fewer pollinators.’

Anyway, working with thousands of citizen scientists is bound to lead to variability. Not everyone will sow, measure or report exactly as per the guidelines. ‘We deliberately give the people taking part plenty of freedom so that the project fits their garden,’ explains Florissen, ‘but that also means there are lots of variables. Even so, it’s enormously valuable: we get data from all over the Netherlands, covering different soil types and a wide range of conditions.’

Jeroen Piël from Blaricum is one of the gardeners taking part. For him, combining science and education is what makes MoestuinMix so special. He volunteers at the Educational Vegetable Garden in Eemnes, which welcomes primary and secondary pupils — and even toddlers this year. The garden is taking part in MoestuinMix for the third time this year. Piël shows visitors how he is playing his part in the research. ‘We measure how tall the plants get, when they flower and how many bean pods they have. The children love the idea that this data is being sent to Wageningen.’

The findings from MoestuinMix are also used as input for further research. The CropMix team wants to take the promising combinations and set up experiments under controlled, field-like conditions. ‘Then we can see which combinations can be scaled up for commercial cultivation,’ explains Florissen. Delamore also hopes that the large volume of new data from 2026 will yield more precise and detailed information. ‘Ultimately, we want to be able to give advice that growers can use in practice.’

For farmers, mixed cropping can be a way to spread the risk – a strategy that is becoming ever more important in a changing climate. ‘Monocultures are inherently vulnerable,’ says Florissen, ‘but combining crops lets you minimize the damage caused by pests or extreme weather.’

It is inspiring for participants to see how their small contributions become part of a bigger picture. ‘I think it’s brilliant that a mere vegetable gardener like me can help in research that could shape the future of agriculture,’ says Piël. ‘Even if it’s only on a small scale.’