Plant Potting Mixes
Plant potting media and fertilizers.
Over the years I have collected lists of ingredients and the added fertilizers for different potting mixes used in plant production nurseries. These are listed at the end of the article for those plants people who would like to make their own potting media mixes.
Many home gardeners and hobby plant propagators prepare their own potting mixes from what ingredients they have on hand and by trial and error. Judging the suitability of the mix by appearance, feel and smell and if this is providing good quality plants, it is gardeners experience that should be followed.
But much researched has been conducted over the years to ensure potting mixes are designed so that they perform well, are reliable and don’t have variable performance caused by too much fertilizer, incorrect pH or lack of aeration.
In the 1930s the John Innes Institute in England (JIC, 2020) researched and developed several potting mixes using loam, coarse sand and peat.
John Innes seed raising mix:
2 parts loam : 1 part coarse sand : 1 part peat
To each cubic metre add 1.2 kilograms superphosphate and 600grams calcium carbonate (garden lime).
