Hortensia

Yes, but as you can see on leaves, it is missing something- I guess nitrogen?

Katarina - the leaf discoloration is caused by iron deficiency. Hydrangea likes acid soil. If your pH of your soil is neutral or alkaline the plant is not able to take the iron it needs. Would recommend a special fertilizer - it should solve the problem.

Kasia, I used fertiliser for Hydrangeas in April and and the end of May. Even added peat....

Maybe apply it now? Can't think of anything else really.

I do not think that fertilisation can be done every two weeks. It says at the beginning of the growing and then blooming season. Plus neighbouring Hydrangea is pretty normal. Enigma.

Hmm - strange, really;-)