My wife wants a blue hydrangea which she intends to keep in a large tub. How do I get one which A) is blue & B) stays blue. All those in this area are pink(ish)
I think the colouring of the hydrangea depends on the acidity/alkalinity of the soil in which they are grown.
Sadly I cannot now remember whether it is the same as for litmus paper (acid=pink, alkali=blue) or the other way round.
Maybe you could experiment with more peaty or more limey soils...
the local florist told me to bury rusty nails around it to keep it blue.. but I didn't buy one. she said the ones in the shop were struggling to stay blue.
I got the Hydrangea blue powder from a garden centre in London... I have used it for 2 years now on 5 hydrangea plants I have. and its been really successful.. I get light blue,,,navy,,,purple,,,lilac (one particular plant seems to have flowers with different colours - pink, pale blue, lilac)...But each plant seems to come up with a different shade of blue - the purple is great...