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.

JOHN INNES SEED COMPOST:

The traditional mix for sowing almost any type of seed, with sufficient nutrient for early development. May also be used for rooting soft cuttings.

2 sterilised Loam
1 Peat
1 Sand

The loam and peat is put through in 9mm (3/8 in) sieve.

For each cubic metre of mix, add

0.6kg ground limestone
1.2kg superphosphate

JOHN INNES CUTTING COMPOST:

1 Loam
2 Peat
1 Sand

No added fertiliser

JOHN INNES POTTING COMPOST No.1:

for pricking out or potting-up young seedlings or rooted cuttings. This composts has a carefully balanced nutrient content to suit most young plants.

7 Loam
3 Peat
2 Sand

For each cubic metre of mix, add

0.6kg ground limestone
1.2kg hoof and horn meal
1.2kg superphosphate
0.6kg potassium sulphate

JOHN INNES POTTING COMPOST No.2

for general potting of most house plants and vegetable plants into medium size pots or boxes. Contains double the amount of nutrient in JI No 1 to suit established plants.

7 Loam
3 Peat
2 Sand

each cubic metre of mix, add

0.6kg ground limestone
2.4kg hoof and horn meal
2.4kg superphosphate
1.2kg potassium sulphate

JOHN INNES POTTING COMPOST No.3

a richer mixture for final re-potting of gross feeding vegetable plants and for mature foliage plants and shrubs in interior planters or outdoor containers.

7 Loam
3 Peat
2 Sand

each cubic metre of mix, add

0.6kg ground limestone
3.6kg hoof and horn meal
3.6kg superphosphate
1.8kg potassium sulphate

JOHN INNES ERICACEOUS COMPOST:

2 Loam
1 Peat
1 Sand

To each cubic metre of mix, add

0.6kg flowers of sulphur
1.2kg superphosphate

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