There's nothing more frustrating then seeing an old church patch of hydrangeas that have been cut back to the same point for the past 60 years and are just overflowing with dead canes. I've seen so many of those here in south Brooklyn lately, I need to post some pictures at a later date. Any dead canes should be removed in late winter/early spring. Ours were removed closer to late winter this year but I'm blaming all of the early leaf out on that.
One of the most important thing about growing hydrangeas is knowing which type of hydrangea you have. Different hydrangeas require different pruning times since some will flower on new wood and others will flower on old wood.
Hydrangea macrophyllas and Hydrangea quercifolia both bloom on old wood. Macrophylla makes up the mophead and lacecap hydrangeas. While quercifolia has big oak shaped leaves. Hydrangea arborescens and has greener stems and blooms on new wood. Hydrangea paniculata also blooms on new wood so you can prune at any time really (just don't cut off all the new blooms once they develop).
Oakleaf hydrangeas are the most forgiving of the group. They better toleration dry soil and I really think they have the best fall color of the group. People forget to prune arborescens all the time and they eventually become these green woody messes. I'm also not crazy about their gigantic blooms. Mopheads have been one of my favorites this year. Lady in Red hydrangea has impressed me with its red stems and decent fall color, but the blooms have been incredible this year.
It is true that the pH does affect the coloring aspects of the flowers but different cultivars do tend to lean towards certain colors. Hydrangeas do best in part shade since they tend to wilt and burn in full sun. The runners can be annoying so try to cut them off in the spring before you end up with 5 small plants around it.
In the meantime I have some pictures I took of these babies during our New York heatwave. Its been about 100 degrees for the past two days so these hydrangeas have been wilting like mad.
Hydrangea quercifolia, Oakleaf hydrangeas
Lacecaps in both pink and blue.
Variegated lace caps
Hydrangea quercifolia 'Snowflake' is another one of my favorites. The green in the flower and the doubles are just so nice.