The pennys and the blue flowers

While I was in New Zealand , I`ve noticed so many beautiful blue hydrangea , I don`t really like the hydrangea but the color was too good not to notice them ,
then while i was in my aunty garden I noticed lots of copper pennies under the hydrangea plants , so I`ve asked and she reply that the copper is the secret of the
blue flower ......

I`ve been looking around , but couldn`t find any advice about it , been reading about alluminium that lower the soil ph , but never about copper ....

will that work with other blue flower????

that`s the blue I`m talking about

 

pardon for my English , pennies and not pennys

 

I have heard of the copper - was copper wire - but pennies sounds interesting and easier for me. I buy the hydrangea colourant for some of my pink hyd's in pots. Have wondered myself whether the colourant would work on other plants - not tried it yet though.

S

 

We used to use rusty nails when I was a kid ... dunno if the chemical mechanics were not properly known back then? but nowadays it is considered that Aluminium is the metal that makes Hydrangeas blue, and being on an acid soil facilitates uptake of Aluminium, so putting Aluminium sulphate around the plants (and watering with rain water) is the easiest way to make them Blue, short of having acid soil.

This isn't a feature of Blue flowering plants per se, but something specific to Hydrangeas (and probably some other plants too ... I've forgotten the technical name of the feature that makes they colour Pink on Alkaline and Blue on Acid soils)