Nothing says summertime like big, bold hydrangeas. Known for their abundant and showy blooms, hydrangeas make enough impact in the landscape to last all season, along with stunning foliage that creates a secondary color show in autumn. New to hydrangeas? Consider the main groups beloved in North American gardens. Bigleaf, or macrophylla, hydrangeas, aside from their impressive foliage, are known for large, rounded flower clusters. It includes two main varieties: mophead hydrangeas, which have dense, ball-shaped flower heads, and lacecap hydrangeas, which feature flat flower heads with a ring of large flowers surrounding smaller ones. Some of the showiest hydrangeas fall into this group, and some feature colors that shift due to pH. Panicle hydrangeas feature elongated flower clusters that start out white or green, and gradually turn pink or even deep red as they mature. They are typically more sun-tolerant and taller, sometimes even growing in a treelike shape. Oakleaf hydrangeas show off large, cone-shaped flower clusters and distinctive lobed leaves that resemble oak leaves. They often have attractive fall foliage color, turning red or blazing orange in autumn.