There was a long thread about it on this site last year, but the color in question was yellow. Check out this link. I never got around to trying it so let us know what happens!!....yg

Here is a link that might be useful: Yellow Hydrangeas / Food coloring

It makes for an interesting topic for discussion, but otherwise - not a chance it will affect the coloring of your hydrangeas growing in the ground! There is currently no approved natural source for blue food coloring. The two blue food colorings currently available are petroleum derivatives and the likelihood of these compounds remaining stable in solution in the soil is highly remote. Soil and water are the great garden equalizers and in combination, together with soil organisms, these eventually breakdown all chemical compounds into their elements. Unless you are ready to use copious amounts of food coloring (quarts rather a few drops), this stuff will dissipate into the soil almost immediately, long before being absorbed by the plant roots.

Think about it - if food coloring was in any way likely to change in-the-ground flower color, I'm sure we would have seen all sorts of strangely colored flowers, like kelly green roses, being touted long before now. It is far more likely that the water being used was acidic in pH and that rather than the food color is causing the blue flowers.

Food coloring will work rather amazingly well to change color on cut flowers, however.

thank you two for the feedback. and the interesting link. last year after my endless summers had a nice showing of blue flowers. they later bloomed pink. i'm going to try 'bluing' one. just curious enough to do that. and with time on my hands to watch it. hehe.
if i see any difference in the color. i'll write again and let you know

I tried adding some dye to the soil of a Nikko last year when I was dyeing the yellow flowers. It didn't do anything at all that I could recognize. Perhaps there were reasons like my not using enough or something, but I didn't see any change at all when I added it to the soil.

I think I'd agree with gardengal, that the soil would quickly absorb the food color. I suspect that there's a bunch of little microbe running around somewhere out there with the hottest, yellow cilia and flagella in the neighborhood.

But I don't know yet about using "Bluing", that stuff from the old days to brighten your laundry,... and your hair, too. Someone from this forum emailed me a long time ago and told me that she had known someone who said that they got their hydrangeas to turn blue by adding "Bluing" to the soil.

I don't know, but it looks like you can certainly dye your carnations with the stuff.

The first blue carnations are credited to Mrs. Stewart's Bluing! Freshly cut carnations placed in a vase with a high content of Mrs. Stewart's Bluing in the water will by osmosis carry the blue color into the tips of the petals quickly.

So, you start to wonder......maybe.......

Prussian Blue

Hay

lol....here we go again!!....yg

it will work if you add some alum. sulphate too it!!!!!

How funny to see Mrs Stewart's bluing mentioned here. It's done nothing for my laundry but I just may try it with cut flowers. Thanks! =)

PS I wouldnt try anything like food coloring or Mrs S w/growing plants.

The color is controlled by the pH of your soil. My blue Endless Summers were put in about a month ago and are already nearly pink, still more on the purple side.

I bought some "Hydra Blue" at the garden center when I got the plants cuz I knew our soil would turn them pink. I have yet to use it as it says to wait til fall.

I did have a happy accident however. My husband by mistake dumped about half a bag of fertilizer into the hole for a new rose bush, nearly burned the poor thing to death. However, the water the rose sat in while we exchanged the it's soil was full of the annaerobic material. After we saved the rose I poured that water onto the ES's and new blooms are more blue again. I may snag a shovel full of that "bad" soil back from his garden and put it with the hydrengea's to see if it will help change the soil pH.

I've also found a great way of quickly turning hydrangeas different colors is to just buy a set of colored sunglasses, I have blue, pink, and yellow ones.

LOL...good one....yg