Why change?

Abstract

When plants are grown in containers their roots are restricted to a small volume of compost*, consequently the demands made on the compost for water, air and nutrients are much more intense than those made by border-grown plants which have an unrestricted root-run and an infinitely greater volume of soil in which to grow. It has long been recognised by amateur and commercial growers alike that simply using a garden or border soil in a pot without any improvement to its physical properties or nutrient status will give poor results. Growers have traditionally used such materials as leafmould, decayed animal manure, spent hops, peat, mortar rubble, wood ashes, sand and grit as additives to mineral soils to improve their physical properties. The introduction of the John Innes composts by Lawrence and Newell in the 1930s did much to standardise and rationalise the multitude of materials then being used. Forty years of experience with these composts have shown that, if prepared and used correctly, very good results can be obtained.