What does ‘John Innes’ mean?

We know there can be confusion about what John Innes composts actually are and who he was. In this month’s blog, we aim to answer all the questions you may have about this great heritage range of composts…

Our new SylvaGrow John Innes composts went into production in February and will start appearing on garden centre shelves very soon.

SylvaGrow John Innes Seed Compost, No.1, No.2 and No.3 offer gardeners an exceptional opportunity to use these great heritage composts with an updated peat-free formulation.

Each one is formulated with specialist fertilisers to give optimum growing conditions. Use our SylvaGrow John Innes Seed Compost for propagating, No.1 and No.2 for pricking out and potting on and No.3 for mature plants such as trees and shrubs in containers. All are RHS endorsed and vegan friendly.

Who was John Innes?

John Innes was a 19th century property developer and philanthropist in the City of London. On his death in 1904, he bequeathed his fortune and estate to the improvement of horticulture by experiments and research. The result was the establishment of the John Innes Horticultural Institution, initially at Merton in Surrey. Now, it is an independent, international centre of excellence in plant science, genetics and microbiology called the John Innes Centre and located in Norwich.

How did ‘John Innes’ mixes arise?

The Institution became the first centre for the study of plant genetics in Britain, and as such the researchers needed reliable growing media in order to remove what was a clear source of variability within their experiments. In the late 1930s, after much study by its two researchers, William Lawrence and John Newell, the physical properties and nutrition necessary in composts to achieve optimum rates of plant growth were determined.

They also introduced methods of heat sterilising the soil that eliminated pests, diseases and weed seeds, and which crucially did not cause any checks to plant growth. Two standard formulae were introduced, one for seed sowing and one for potting and they quickly became accepted as the best composts for raising plants in pots.

The John Innes range today

Today, the range commonly consists of a seed compost as well as three numbered versions, No.1, No.2 and No.3, each representing successively higher fertiliser levels. Ericaceous John Innes composts have also been introduced.

Various modifications have had to be incorporated over the years – for instance, the soil in the original recipes came from stacked turves. The thinking here was that soil that supports long-standing lawn or grassland which has been undisturbed for many years, usually has a very good structure, which if handled carefully, could be very useful in a potting mix.

Nowadays it is not possible and nor would it be environmentally sustainable to use loam from stacked turves in commercial production. Also, the plant nutrient sources have been updated to gain the benefits of improved fertiliser technology.

What is the John Innes formula?

The original formula for the John Innes potting mixes was a blend of sterilised loam, peat and potting grit plus an appropriate nutrient base. Environmental concerns surrounding the use of peat are resulting in an increasing number of John Innes brands becoming available with peat-free formulations. The new SylvaGrow John Innes range is one of these. The seed compost version is slightly finer with a lower nutrient level and incorporates sand in place of potting grit.

Who uses John Innes mixes?

Over the years, potting composts have passed through several phases. Soil-based mixes such as John Innes dominated until the 1970s. This was when lighter mixes based on peat took over the market as good-quality peat was readily available from northern England, Somerset and Ireland.

The burgeoning popularity of gardening and the advent of garden centres caused a huge increase in the use of growing media as more and more plants were sold in containers. Lighter mixes were required in order to make the handling and transportation of large quantities of plants more efficient.

The commercial growing industry now uses very little soil-based compost, but John Innes mixes remain a popular choice for gardeners due to their good reputation for ease of use and great results. At Melcourt we are delighted to have developed a John Innes range to join our other SylvaGrow peat-free composts.