Hydrangeas will grow as wide as 8 feet if you let them - but that would be the old fashioned Hydrangeas marcophylla. The new hydrangeas are repeat bloomers like \"Endless Summer' and the more compact \"Pistachio' and these I grow I a bed that is four feet deep. I just prune the hydrangeas back by one half in early spring and because they flower on new wood I enjoy blooms every summer. The old fashioned hydrangeas only flower on 2 year old wood - so if you prune them each year you get foliage and no flowers. I would definitely recommend the new \"Endless Summer\" hydrangeas. One more tip - add some hellebores at the base of your hydrangeas - than you will have blooms in early spring when the hydrangeas still look like bare sticks. Keep growing, Marianne Binetti