The range of strengths gave composts for differing uses:

Seed: For seed sowing of fine seed. Low nutrient value avoids ‘burning’ of seedlings. Assume to be pricked out <6 weeks after germination. Number 1: pricking out/potting rooted cuttings/plants that like a low nutritional content (Calceolaria);

Number 2: general potting compost; Potting on geraniums or hardy stock.

Number 3: final potting compost for crops like Chrysanthemum/Tomatoes. Or for long term specimen plants, Azaleas, Palms, Trees, & shrubs. Bl`

The John Innes range of composts introduced in the 1940s were the first scientifically developed standard composts. Based on partially sterilised loam (Lawrence and Newell). The compost is heavy with a good natural food content (N.P.K. and trace elements), is enriched with fertilisers, the pH is about 6.5, has a natural root zone giving good root stability and clay content which holds on to added fertilisers.