I have never grown hygrangeas so can't help you much with this. I do know that as our soil is alkaline here, your blooms will always be blue unless you do things to make the soil more acidic, then you'll get the pink blossoms. For some reason, I didn't think they like clay soil, but I am not sure. If no one else here in the Rocky Mtn. forum can help you out, check with the folks on the Hydrangea forum right here on GardenWeb. :-)

Holly

I don't know a lot about Hydrangeas either, but a few things.

The standard (mophead /lacecap or macrophyllas) hydrangeas you get in a pot bloom on old wood. With dry cold winters you need to protect that wood or it will die back and you will get a foliage but no blooms. That is what happened to me the past several years and the plants don't grow much since they just get back what was killed over the winter. To protect them I guess you could cover the plant with mulch in the late fall.

Also, the standard potted hydrangea is an acid loving plant so they are iffy if you plant them in akaline soil. I love them so much I tried to ammend, but they have just kind of survived, not thrived. The color changes I understand are achieved with variations in the acid PH, but they still need acid not akaline soil to thrive (which we don't have).

The other varieties like Oakleaf or PeeGee hydrangea fair better in dry (air) and akaline conditions. They also bloom on new wood which is nice because they are determined to bloom every year regardless of protection.

I remember my Grandma had beautiful macrophyllas in her Cheyenne Wyoming yard. Either the soil is more acidic there, or she had a great secret.

I found a page with a better breakdown (see link)

I am wrong on the acid thing based on this page. I don't know where I got that from. Looks like there are other varieties like snowball that are quite showy and hardy down to zone 3.

Here is a link that might be useful: Hardy Hydrangeas