The pair started to investigate the procedure of making seed and potting composts following heavy losses of Primula sinensis seedlings in the 1933-34 season, which were an important experimental plant for JIHI geneticists.
[2] The institution made the formulae generally available, but never manufactured the composts for sale nor benefited financially from their production.
[4] The soil component contains: With amendments of: The potting mixes are used to grow different types of plants depending on their nutrient requirements.
Peat-free John Innes composts may be made by replacing the peat in the recipe with a substitute such as wood fibre, coir, or bark.
[6] These substitutes tend to be less acidic than peat, so a smaller quantity of ground limestone is used to balance the pH level.