it is a specific product to colour hydrangeas blue. Thanks to its particular composition containing also an aluminium salt, it acts on the soil causing the pigmentation of the inflorescence of some sorts of hydrangea (Hydrangea macrophylla).
at the time of plantation mix the content of one spoon (10 g) every 2 litres substratum; for maintenance scatter on the soil or bury the content of one or two spoons; treat once a month until the desired pigmentation has been reached. Then water.