We Brits often mention John Innes (JI) composts. To clarify, these were a set of standard potting soil recipes the John Innes Horticultural Institute invented in the UK for growing plants in containers. We in the UK use the term "compost" for both potting soil mixtures and to mean rotted vegetation, as you in the USA do.
For many years our standard potting mix before mineral composts became fashionable were JI composts with added grit for cactus and succulents. Unfortunately the commercial JI mixes on sale here are now going peat free and adding compost made from rotting garden waste, which is not as good for our plants. These are the JI original formula's you can make yourself instead:-
http://www.gardeningdata.co.uk/soil/joh ... _innes.php" onclick="window.open(this.href);return false;
You will note that JI numbers 1 to 3 are exactly the same mixture, with only different amounts of fertiliser added. These days commercially a normal balanced fertiliser is usually added to the mix rather than the original fertiliser mixture. This was a potting soil recommendation using JI compost from one of our British sites:-
"For the vast majority of cacti and other succulents a suitable mix is John Innes No. 2 or 3 mixed with grit, such as Cornish grit or 3–4mm grit, coarse sand (NOT builders’
sand) or perlite in about equal quantities. For more difficult species and those known to originate from drier areas, the proportion of gritty materials is increased, even to as much as
75% of the total mix."
http://society.bcss.org.uk/images/Cult/ ... atemix.pdf" onclick="window.open(this.href);return false;
These days many have moved to purely mineral composts, but these do need regular fertilisation (including trace elements) since unlike soil based mixes they contain very few nutrients. The hated peat composts that many plants come in are similar in that they are just a medium to hold the roots and contain few nutrients therefore needed to have been regularly fertilised at the nursery where the plants were originally grown. Also they were never allowed to dry out completely in the nursery since peat composts are difficult to re-wet. Unfortunately the retailers you buy them from let them dry out and that's why the compost that has grown a magnificent plant so far has such a bad name with collectors because they then need to remove it and substitute something that re-wets more easily.
Though American collectors hate peat composts, their country actually invented them. It was The University of California that introduced these mixes, just as the John Innes Institute introduced the loam or soil based ones. I remember when the University of California came up with peat based composts to replace JI ones as they were published in one of the early American cactus journals for using with our plants, formula's the British firm Levington more or less copied in the UK.
Here was the University of California Succulent Compost:-
"University of California Succulent (UC) Mix:-
•1 part ground sphagnum peat
•1 part redwood compost
•1 part horticultural sand
•2 parts volcanic pumice
•for every one cubic foot of mix add:
◦5 tablespoons dolomite limestone
◦2 tablespoons gypsum
◦3 tablespoons superphosphate
◦1 teaspoon potassium nitrate
◦1/2 teaspoon potassium sulphate
Again these days that fertiliser mix would usually be replaced with a commercially available balanced fertiliser. UC composts are sort of a JI peat based potting compost without the soil! For the history of potting soils and UC mixes see:-
http://ucanr.edu/sites/EH_RIC/newslette ... 837629.pdf" onclick="window.open(this.href);return false;
