Citric acid can be used to prepare irrigation water and adjust the pH of a diluted fertiliser solution before feeding plants. It neutralises carbonates and bicarbonates and reduces water alkalinity. Over time, highly alkaline water can raise the pH of a growing substrate.

Preparing irrigation water
Check the water’s pH and alkalinity. If acidification is needed, use the irrigation-water pH target recommended for your plant and substrate.

Measure a small amount of water and check its starting pH.
Add a small amount of citric acid to the water and mix thoroughly.
Check the pH with a meter or test strips. Add citric acid gradually, mixing and measuring after each addition until the chosen pH is reached.
Check the pH again when preparing the next batch of water.

Add the acid to the water. Avoid contact between the solution and your eyes or skin.

Adjusting fertiliser-solution pH
If you use citric acid with fertiliser, first mix the fertiliser with water and check the pH. Then add citric acid as needed.

Helps release phosphorus plants need
Citric acid helps dissolve sparingly soluble calcium phosphates and release the phosphorus bound in them. In a cucumber-seedling trial, applying it to the roots helped plants accumulate more phosphorus in their roots and increased the dry mass of the above-ground parts. This benefit was observed under limited phosphorus availability – in a sand-and-perlite substrate containing tricalcium phosphate. Study, 2023.

Cleaning garden equipment
An aqueous citric-acid solution helps remove limescale from empty, acid-resistant equipment. Use it in accordance with the care instructions for the item or equipment.

Flower pots and vases. Apply the solution to deposits, leave it to act and rinse thoroughly.
Removable spray nozzles. If the instructions permit citric acid, remove the nozzle, clean it in the solution, rinse it and refit it.
Iron deposits in irrigation drippers. Citric acid helps dissolve them from removable, acid-resistant parts. Remove the drippers, clean them according to the equipment manufacturer’s instructions and rinse thoroughly before reinstalling.
Hydroponic equipment. Remove the plants before cleaning. Clean the empty reservoir and removable parts according to the manufacturer’s procedure, combining the citric-acid solution with mechanical cleaning. Rinse thoroughly before putting plants back.

Do not use to clean marble, slate, granite, enamel or aluminium.

Chemical composition
Citric acid. Chemical formula: C₆H₈O₇.