GROW Experiment topic

Experiments(Last edited )

Welcome to the GROW Experiment topic!

In this topic you can ask questions, share your experiences, and meet others taking part in experiments in your growing space.

Try a polyculture experiment in your growing site

Do regenerative practices work at the smaller scale? And if so, how, and where? Regenerative practices are approaches that can help improve, or ‘regenerate’, soils and ecosystems - we are focussing on regenerative practices used while also growing food plants.

Through conversations with people who have done previous GROW courses, and through reviewing scientific literature and key information, we found out that companion planting and growing polycultures is an area where there is a lot of interest, but also a lot of conflicting information and uncertainty. We know that many of these regenerative approaches to growing are practised at the smaller scale, and that individual growers can find these beneficial. So in 2018 GROW developed an experiment to investigate these practices.

Polycultures – growing several crops together at the same time – have been shown to have benefits in terms of crop yield, resilience to pests and disease, and enhancing wider biodiversity. However, mixes of three or more crops have not been extensively studied and much remains unknown. In 2018 GROW brought together growers and scientists to investigate these practices through citizen science. The Great GROW Experiment aimed to compare harvest quality and yields from a) three crops grown together in a polyculture, with b) each crop grown separately in a monoculture. The three crops were:

  • round climbing beans (Phaseolus vulgaris “cobra”)
  • spinach (Spinacia oleracea “matador”)
  • radish (Raphanus sativus “cherry belle”)

These were grown together in a one square metre plot with 9 bean, 36 spinach and 80 radish seeds planted. The same number of seeds were also sown separately in plots of 1 metre long by 60 cm (beans), 1 m by 40 cm (spinach) and 1 m by 30 cm (radish). If you would like to know more about the Experiment design take a look at our blog.

The experiment was developed to answer one main research question:

  • Is there a difference in yield of beans, spinach and radish when grown as a polyculture compared to when grown as monocultures?

GROW Experimenters, including people who participated in the Citizen Science: Living Soils, Growing Food online course, worked together to answer this question. They found that overall the polyculture combination had significantly greater yields than the monoculture. The polyculture yielded an average of 3.06 kg per square metre (with a standard error of 0.43), and the monocultures together yielded an average of 2.28 kg per square metre (with a standard error of 0.32). In addition, 67.7% of participants found that in their own growing space, growing the crops together yielded more. However, that means that nearly a third of people had more success with the monoculture! Clearly, there is more to learn about how and when each approach works best.

Although GROW won’t be collecting data this year, you can set up and run your own polyculture Experiment and discover what works in your own plot. You could also encourage other growers in your community garden or allotment to take part and compare your results together. Experiments are even more valuable when several people take part, as we can be more sure results are not due to chance. Instructions for the Polyculture Experiment can be found here. These will guide you how to set up the experiment, understand your growing site and take measurements.


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