Soil pH for Succulent Plants

The intensity of the acid/alkali reaction of soil or compost is expressed in terms of pH units, representing the negative logarithm of the concentration of hydrogen ions.
 
Most plants grow at their best when grown in soil with a pH range which best suits them. Most cacti and other succulent plants grow well in slightly acidic soil around pH6. A few succulent plants grow naturally on limestone soils with a basic reaction, but an alkaline soil is more likely to kill plants than a slightly acidic one.
 
If you wish to test the pH of your soil mix or water supply, affordable pH meters can be obtained in many garden centres.

Very strongly acidic soils can be improved by adding dolomite of lime (ground limestone). Very alkaline soils can be improved by watering with slightly acidified rainwater. Add very small amounts of citric acid crystals or one or two drops of hydrochloric acid. Check with a pH meter before use. Alternatively add some horticultural peat (typically pH4) to the mixture. Rainwater in or near cities may be naturally acidic.