Hydrangeas need fertilizer in spring - which products are suitable for this. Fertilizer also helps species that are cut back in spring to sprout new plants or form flowers.
Organic fertilizers such as rotted cow manure, cattle dung pellets or horn shavings are well suited for hydrangeas. The color of the flowers also plays a role: If you want a blue color when the farmer's hydrangas are predominantly pink, you have to use alum or a special fertilizer containing aluminum sulfate.