John Innes Potting Compost The recipe for this was originally worked out in bushels and even now in some establishments that mix a lot of their own, bushel boxes are still being used as a measure. I will give the original formula in bushels. Bearing in mind that a bushel is eight gallons it should be easy enough to use a bucket as a measuring container. A bushel box is 22 x 10 x 10 inches or 55 x 25 x 25 cm.
Number One is a weakused for pricking out or plants which do not require much fertiliser. Number Two is normal potting compost strength. Number Three is a strong potting on compost for very hungry plants such as and .
Peat is usually medium grade moss peat which has been put through a rough sieve to get rid of large lumps. However half moss and half sedge peat is acceptable. Always moisten peat thoroughly before mixing the compost.
Sterilised loam 7 parts by bulk
Moss Peat (well moistened) 3 parts by bulk
Sharp sand or potting grit 2 parts by bulk.
To this is added John Innes Base fertiliser as follows:
No. 1 per bushel 4 oz J. I. Base and ¾ oz Chalk or Ground Limestone
No. 2 per bushel 8 oz J. I. Base and 1-½ oz Chalk or Ground Limestone
No. 3 per bushel 12 oz J. I. Base and 2-¼ oz Chalk or Ground Limestone
John Innes Base is composed of the following:
Hoof and Horn (1/8 inch grist) 2 parts by weight (13% N)
Superphosphate of Lime 2 parts by weight (18% P)
Sulphate of Potash 1 part by weight (48% K)
John Innes Seed Compost
Sterilised loam 2 parts by bulk
Peat 1 part by bulk
Sharp sand (up to 1/8 inch diameter) 1 part by bulk
To this add 1-½ oz Super-phosphate of Lime and ¾ oz Ground chalk or Limestone per bushel.
Modified John Innes for Potting
I find that some bought in John Innes can become very compact in the pot and can cause problems with over watering. I like to improve it in the following way:
John Innes No. 3 3 parts by bulk
Peat 1 part by bulk
Sharp sand 2 part by bulk
If modifying John Innes 3 for, bulbs or other plants which like a well drained compost use an extra one part of sharp sand instead of half.
There are two other home-made potting compost recipes which I have found to be good which use Vitax Q4 as the fertiliser.
Peat 3 parts by bulk
Sharp sand or grit 1 part by bulk
Lime 4-½ oz per bushel
For a number one 4 oz Vitax Q4 per bushel
For a number two 8 oz Vitax Q4 per bushel
Peat 5 parts by bulk
Sharp sand or grit 2 parts by bulk
Loam 1 part by bulk
Lime and Vitax Q4 as above.
Orchid grade bark 4 parts by bulk
Perlite 1 part by bulk
Charcoal 1 part by bulk
No fertiliser is added. This is applied as a liquid or foliar feed.