Over winter green manures are plants grown to protect the soil over winter. The standard mix of grazing rye and vetch that is frequently grown is very dependable but it can be tough to incorporate in the spring, especially for gardeners practising no-dig methods. The aim of this experiment was to compare an alternative green manure mix (‘Gardener’s mix’) containing 5 different species (Vetch, Forage Pea, Crimson Clover, Phacelia, Flax) with the standard grazing rye and vetch mix at a range of locations around the UK.

Around 80 people took part in the trial sowing small plots of each green manure mix in back gardens around the UK in September 2022 and 2023. They incorporated them the following spring and made observations to their growth and assessed how easy they were to incorporate.

In both 2022 and 2023, the Gardener’s mix established very well in the autumn and covered the ground well. However in 2022, the mild autumn resulted in a large amount of lush growth that was then killed off by a sudden frost in December. There was some recovery of growth in early spring. Having a mix of species helped to promote adaptability: the phacelia grew well initially but was killed off, then the slower- growing but more resilient crimson clover started to fill out the gaps. In 2023, there were less severe frosts, so the Gardener’s mix showed better survival into the spring, although it was starting to break down by the spring at the time of incorporation.

In both 2022 and 2023, a high proportion of participants used a no dig ‘chop and drop’ technique respectively to incorporate their green manure, demonstrating a strong interest in “no dig” methods of growing. The Gardener’s mix was also much easier to incorporate than the standard rye-vetch mix which contained a lot of tough material that many participants had to remove from the soil and add to the compost heap.

In conclusion, the Gardener’s mix was definitely easier to incorporate but was killed off by heavy frosts so may not protect the soil all winter in colder areas of the country.

Read the full report here.