Big leaf hydrangeas grow 4 to 6 feet tall. They bloom on old wood and take on a more shrubby structure. These are the classic blue hydrangeas. Varieties, such as 'Nikko Blue', produce large, deep blue flowers (depending on the soil pH) from mid-summer until fall. They are generally hardy in zones 5 and warmer.
In zones 4 to 6, try the newer 'Endless Summer' type hydrangeas. These have been bred to flower on old and new wood, so even if the plant dies back to the ground in winter, the new growth that emerges in spring from the roots will eventually flower. Newer selections of this type, such as 'Bloom Struck', have proven to be more reliable bloomers than the original 'Endless Summer'. There are also lacecap versions of this bigleaf hydrangea, such as 'Twist n Shout', that offer a lacier looking flower.
Panicle hydrangeas bloom on new wood, but grow into a large shrub or small tree. The most famous of these is the 'PeeGee' hydrangea. Panicle hydrangeas are often planted in cemeteries, perhaps because they're so carefree and bloom consistently each fall. Newer selections, such as 'Limelight' and 'Bobo', feature flowers that start out white, but quickly fade to pink or burgundy. They are attractive plants in the landscape and the flowers are easily dried for indoor use. Panicle hydrangeas are also very winter hardy and can range in size from 4 feet to 15 feet tall depending on the variety.
Oakleaf hydrangeas have oak-shaped leaves on 5 to 8 foot tall shrubs. Like the panicle types, the flowers start out white and fade to pink in late summer. This American native is noted for its large flowers and beautiful fall foliage color. It's hardy in zones 5 to 9.
Finally, the climbing hydrangea looks different from all the other types mentioned. This woody vine is hardy to zone 4 to 8. It slowly grows up to 30 feet tall. It produces white, lacy, fragrant flowers in early summer and grows well in part to full shade. The exfoliating bark is attractive in winter after the leaves drop. It takes time to get established, but once growing will thrive for years.