Last summer my hydrangea had pink flowers - the year before they were blue.
I understand they become blue with increased soil acidity.
Can anyone tell me how to achieve this again?
Aluminium sulphate - you can get it from garden centres. Iron nails etc. DO NOT work!
Verdun, You may have literally hit the rusty nail on the head.
The hydrangea is in the soil next to an outbuilding which has a rusty gutter which leaked badly very close to the hydrangea, but then the end piece fell off the gutter so last year the water leaked out at the end instead.
The metal gutter is due to be replaced with a plastic one, so perhaps instead of taking the old one to the dump I'll just "plant" it next to the hydrangea.
I've no idea what variety it is. It's been here years and has been shades of pink through lilac to a light blue.
We have an acid soil, but the hydrangea roots are right up against the bothy foundations so it probably gets varying pHs depending on weather.
What is the blueing agent and where can I get it?
Sorry Verdun, I sent my post same time as you.
Hi Gold1locks. Sorry missed your reply. Is Aluminium sulphate the blueing agent Verdun mentioned?