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Where in the World: Loam-based Compost

Published on June 12th 2018

by pippa.churcher. All rights reserved

Potting Mix

Most growing media are soil-less using a peat or peat free alternatives as the main ingredient for the growing media formulation. There are advantages to both types of formulation.
John Innes can feel a little confusing as there are several different ones you can use, each have their own specific recipe and best use.

What is a loam based compost?

John Innes compost formulation was invented in the 1930’s by John Innes.There are several different recipes, ranging from seed sowing, potting and then One, Two and Three all specially created for a range of different tasks eg, growing on seedling to potting trees and shrubs in containers.
The basic ingredients in all John Innes compost are:
  • Sterilised Loam although soil is used too, due to access to being critically low.
  • Sphagnum Moss Peat used in the original recipe although peat free media is a viable alternative.
  • Sand
  • Fertiliser trace elements the qualities vary for each recipe.
The advantages of using a loam based compost is the stability. Loam compost will retain its temperature and fluctuates less meaning that plants can establish roots quicker. For containers, the added weight of the loam means the plant is less likely to blow over.

Different Types

John Innes Seed compost
Used for seed sowing and for stem cuttings until the seeds or cuttings have roots this formulation has low fertiliser. If you want to make this at home the ingredients are (all ‘parts’ are by volume):
  • 2 parts by loose bulk medium sterilsed loam
  • 1 part by loose bulk good peat or peat substitute
  • 1 part by loose bulk coarse sand
To each 9-litre of the mixture add:
  • 10g (1/3oz) superphosphate
  • 5g (1 teaspoon) ground chalk
John Innes potting mix
All of the potting composts use a base, this can be soil (loam) based and a John Innes fertiliser base.
Soil mix
  • 7 parts by loose volume medium sterilised loam
  • 3 parts by loose volume good peat or peat substitute
  • 2 parts by loose volume coarse sand
Fertilser mix (John Innes Base)
  • 2 parts by weight hoof and horn meal (or 2/3 of a part by weight Nitroform*)
  • 2 parts by weight superphosphate
  • 1 part by weight sulphate of potash
Then the compost breaks down into another batch of recipes for numbers one to three.
John Innes Number One
Used for pricking out, potting on young plants and newly rooted cuttings. This is best used for short term potting, anything that will be being transplanted relatively quickly.
To the base ingredients above add to each 9 litre of soil mix:
  • 28g (1oz) John Innes Base
  • 5g (1 teaspoon) ground chalk
John Innes Number Two
Really good for houseplants and vegetables as it has twice the amount of nutrients than John Innes Number One has.
To each 9-litre of soil mix add:
  • 56g (2oz) John Innes Base
  • 10g (1/3oz) ground chalk
John Innes Number Three
For long term plantings such as shrubs and trees. Number Three is also good for hungry plants such as Tomatoes and Chrysanthemums.
To each 9-litre of soil mix add:
  • 84g (3oz) John Innes Base
  • 15g ground chalk
Hopefully, this has helped a little. Just remember that loam based composts are heavier, take a little longer to warm up but once warm retain their temperature for longer and are great for long term pot planters.

Give it a try, you don't have you make your own you can buy a bag from any good garden centre or the Candide Marketplace.

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