Cannot be so. Pennies are made of zinc, aluminum ions are what affect the color of hydrangea blooms. Actually it is plant cellular pH that determines bloom color, not soil pH. Lowering soil pH makes aluminum ions readily available for plant uptake where it bonds to pigments in the blooms. Here is a post I left on the Botany Forum awhile back. It might be a little technical for new gardeners on this forum, but the general concept is easily understood:

"Three different pigments - chlorophyll, flavonoids, and carotenoids - mixed in different proportions, give color to plants. By mixing and matching the three pigments, an endless variety of colors can be created. E.g. most reds are the result of mixing orange carotenoids with magenta flavonoids. Cellular pH (not to be confused with soil pH) has a profound effect on plant color.
Even most experienced gardeners think that lowering soil pH produces blue blooms in hydrangea. Technically, it is only a part of the equation. Lowering soil pH makes aluminum ions more readily available for plant uptake. The aluminum is then available to bond with pigment compounds (anthocyanin, the colored component of flavonoids) changing the way color is reflected. Our perception is blooms changing from pink to blue.

The anthocyanidin group is what makes apples, autumn leaves, roses, strawberries, and cranberries red. They make blueberries, cornflowers, and violets blue. They also make some grapes, blackberries, and red cabbage purple. One of the things that changes the color of anthocyanins
is the level of acid or alkali (the pH) in the cell surrounding the pigment. As cellular pH increases, the pigment changes structure and reflects different wavelengths of light. The anthocyanin reflects bright pink in acid cell environments, reddish-purple in neutral and green in more alkaline cells.

Since actual nutrient availability and possible nutrient "lock-up" or overload due to soil pH can also have an impact on cellular pH, it's a good bet that having your soil professionally tested for pH and to see what nutrient problems there might be would be a good first step to definitively identifying the cause of the changes you observe."

Al

Oops! The last paragraph has no bearing on this thread. Most have probably already disregarded the whole post, but in case you haven't, & made it this far, please disregard the last paragraph. ;o)

Al

Well, actually I have a neighbor who has the most beautiful dark purple hydrangeas that IÂv eever seen, and when I asked how she got them that color she said she tills pennies into the soil every year and has for the last twenty years. So, ya never know. Also, she works at the Atlanta Botanical Gardens.

As was said, the pennies have nothing to do with the color. Instead, the annual tilling disrupts the roots and, thus, inhibits the natural development of the color of what people call the "flowers." Left to its own devices, the flowers would be within one of two color ranges -- pinks or blues.

What color are you hoping for?

I thought pennies were copper.

"Today's pennies (since 1982) are made from coin blanks made of 99.2% zinc and 0.8% copper, with an outer plating of pure copper."

http://www.faqfarm.com/Q/How_are_pennies_made_and_what_materials_are_used

Terran

Here is a link that might be useful: How are pennies made...

Change to what color? How much should you use? Does it matter what the pH of your soil is? Will this change the pH of the soil? What's in Pickling Lime? Will too much harm the plants?

I think calcium is the primary ingredient in pickling lime. okay - I looked it up: Pickling lime is food grade calcium hydroxide. What it does is elevate pH and maintain calcium.

I've noticed that hydrangeas in soil with an 'elevated pH' seem to bloom in the pink shades -- including Nikki. Check link for more info on hydrangeas' colors.

Oh, and I don't really think tilling could affect the blossom color unless that action disturbed some sort of leaching substrate which could change the chemical balance of the soil, which in turn might affect the pH balance which would affect the aluminum uptake, which might affect the color -providing it wasn't a white hydrangea to start with. OTOH, if I till some cottonseed meal into the soil around Nikki, it just *might* bloom bluer next year; but if I tilled aluminum sulfate into the soil, Nikki would definitely have blossoms in a bluer shade.

Here is a link that might be useful: hydrangea color