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pH value and cannabis plants

What is the best pH value for a cannabis plant?


You should regularly check the pH value of the environment your cannabis plant is growing in. At grow shops and regular garden centres you can easily find a testing kit.

The pH indicates the acidity of a solution. pH stands for potential hydrogenium and indicates the hydrogen ion concentration of the water. A neutral water solution has a pH of around 7. A pH below 7 means the solution is increasingly acidic (down to 0) while a pH above 7 (up to 14) means basic or alkaline.

You water must have a pH between 5.8 and 6.0. Between these values nutrient uptake is most efficient.

Hard water (with a pH higher than 7.4): you’re best off adding a pH-minus powder or liquid. This acidic granule neutralises the alkaline components that are the cause of the water’s hardness. Regularly check the pH!

Soft water (pH under 7): adding pH-plus powder or liquid, baling soda raises the pH above 7.

From pH 14 to pH 0

  • pH 14: caustic soda solution (1 mol/l)
  • pH 13: caustic soda solution (0.1 mol/l)
  • pH 11.5: domestic ammonia
  • pH 10.5: soapsuds
  • pH 8.5: seawater, intestinal fluid
  • pH 7.4: human blood
  • pH 7: pure water (neutral)
  • pH 6.7: milk
  • pH 6: rain water
  • pH 5: lightly acid rain
  • pH 4.5: acid rain, tomato juice
  • pH 3: domestic vinegar
  • pH 2.5: cola
  • pH 2: stomach acid, lemon juice
  • pH 1: sulphuric acid (battery acid)
  • pH 0: hydrochloric acid (1 mol/l)

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