Hydrenga

[warpig3]

I recently bought a hydrenga called Zorro Blue. It was the most fantastic blue colour. When I got it home I replanted it into a larger teracotta pot using ordinary compost. The colour has now changed to a manky washed out blue, a pale blue and some pinky/purple. Can anyone suggest anything I could put into the soil to give it back its blue colour?

Thanks
warpig

[Hawkwalk]

Old rusty nails were often tried in times past, to turn flowers blue. It was not totally wrong as hydrangeas do need iron, but there are better ways. To achieve good blue flowers, aluminium must be present in the soil which must also be acid, and yes, you need iron as well (preferably in sequestered form, unlike nails) to make the aluminium available to the plant. You can obtain hydrangea colourant powder in any garden centre, and if you have or can create acid conditions, you can have beautiful blue hydrangeas.

[Food Fairy]

You need to plant a blue hydrangea in ericaceous potting compost to keep it blue. Chances are your soil's limey and they need alkaline.
Best Regards
Jaquelyn

[warpig3]

Wow, that was quick! Thank you, will check out the garden centre for a colourant and keep the erincaceous compost in mind when/if I repot it.

cheers
warpig

[Noweia]

Hydrangeas need copper for blue flowers - as others have pointed out, a special compost is the best bet.

[sowerbutt]

Did any of the suggestions work - I have the exact same problem, same plant,