Hydrangeas and rusty nails

[NSB]

Has anyone heard of this before?

When planting blue hydrangeas make sure you plant them with a couple of rusty nails - this keeps the colour!!

[Jaxom]

Rusty tin cans also used to be used years ago. Dig up your grannies hydrangeas and you'll find the remnants of ten to twenty tins. As I understand it you can change the colour of a white hydrangea this way. Nowadays hydrangeas have more hard and fast colours due to growers developing their strains.

[Palustris]

This is actually a fallacy, iron has little or no effect on the colour of a hydrangea flower. If you want to keep a bluehydrangea a good blue, then you need to make sure it is growing in acid soil, or add Aluminum sulphate to the soil (sold as Blueing compound). Actually A. phosphate is better but harder to buy. Pink/Red colour is better in alakaline soil. A white hydrangea stays white in either kind of soil. Changing the acidity level of a soil does not change the colour, it only deepens or fades the underlying colour.
The colour of a flower can vary on an indiividual plant and from year to year and can take up to 3 years after planting to settle down.
I have just finished reading a monograph on Hydrangeas with some very interesting proper scientific research done into colouration etc.
Now if the H. macrophylla varieties about which we are speaking would only grow and flower in my garden I could be happy.

[Snadger]

Surely Iron Sulphate has an acidifying affect on soil?

Sulphate of iron plus sulphate of ammonia (which also has an acidifying effect) + sand are the basic ingredients of lawn sand which is also.................you guessed it, very acidifying!

I would imagine the tin can and rusty nail scenario stemmed from the use of Iron Sulphate, but I aint sure whether tin cans and rusty nails can turn into it without other processes being involved?

[Two_Sheds]

I saw a hydrangea with blue and pink flowers on it at East Ruston (Norfolk). Also pink, blue and white plants were all growing together in the same bed.