John Innes Composts

John Innes is not a manufacturer of compost, they are a range of composts developed at the John Innes Institute, named after John Innes, a nineteenth century property and land dealer 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 Research Institute initially at Merton in Surrey, but now located at Norwich.

The essence of these composts from today's point of view is that they are based on loam.

There are several formulae, depending on the use of the compost:

• JI Seed Compost is for sowing seeds;
• JI Cutting Compost is for rooting cuttings;
• JI No 1 Potting Compost is for pricking out young plants;
• JI No 2 Potting Compost is for potting on;
• JI No 3 Potting Compost is for established plants and shrubs;
  and
• JI Ericaceous Compost is for plants which cannot tolerate lime.

The Ingredients

The function of each of the ingredients in John Innes is briefly as follows:-

Loam

Loam is the most important ingredient in the compost as it provides the main "body" of the compost. It also forms the base of plant nutrition by supplying clay, which has a cation and anion exchange capacity, that is, it absorbs and releases plant nutrients as required. Loam also contains essential micro-elements and some organic matter which provides a slow release of nitrogen to the plant.

Peat

Sphagnum Moss Peat in the John Innes Compost increases the total porosity and improves both the aeration and the water-retaining capacity. Peat decomposes slowly into humus.

Sand

The coarse sand or grit is used as a physical conditioner to allow excess water to drain from the compost and thus prevent water-logging. It also helps to provide stability for larger plants.

Fertiliser

The compound fertiliser in John Innes Compost provides a wide spectrum of plant nutrients needed for balanced growth, including :-

• NITROGEN - for top growth
• PHOSPHATES - for root growth
• POTASH - for flowering and fruiting
• TRACE ELEMENTS - for optimal growth, colour and (where appropriate) flavour

Nutrients are typically sufficient for 1-2 months of growing, after which time additional proprietary feed should be given.  

The mixes

All ingredients of the main constituents are by volume.