With the arrival of summer, hydrangea season begins! These beloved landscape plants are easy to grow, long-flowering, and bothered by few insects or diseases (deer is another issue!). There are five main types of hydrangeas. Some are small trees, others shrubs, and one type is a climber, happily scaling up strong structures.
Types of Hydrangeas:
Bigleaf Hydrangea (Hydrangea macrophylla)
Bigleaf hydrangeas are very popular with gardeners for their large flowers and deep green leaves. With cultivars like Incrediball, the blooms can grow a foot across but most have flowers that grow six to ten inches in diameter. There are two categories of Bigleaf hydrangeas: Mophead and lacecap. Mophead’s are common landscape plants producing huge rounded flowers in shades of white, pink, blue, or somewhere in between. The flower colour for some depends on the pH of the soil and gardeners often adjust their soil pH to alter the flower colour. A common question is ‘why doesn’t my hydrangea bloom?’ This is a question that usually comes from gardeners growing mophead cultivars. This is because most mophead hydrangeas produce flowerbuds on old wood from the previous season. In many parts of Canada, winter cold damages the flowerbuds resulting in no flowers. About a decade ago the Endless Summer series of mophead hydrangeas was introduced. These plants produce flowerbuds on old and new wood so flowering is now much more reliable. The second type of bigleaf hydrangea is lacecaps. Varieties like Blue Billow and Tiny Tuff Stuff enchant gardeners with their delicate, flat-topped flower clusters. Lacecap hydrangeas make excellent shrubs for a woodland garden or plantings under tall deciduous trees.
Panicle Hydrangea (Hydrangea paniculata)
Want a reliable, resilient, and long-flowering hydrangea? Plant a panicle hydrangea. These small trees bloom year after year, no matter the winter weather. Why? They produce flowerbuds on new growth. Plus the plants themselves are also very winter hardy, thriving down to zone three. And those flowers! Panicle hydrangeas have large, cone-shaped flowers in a range of dramatic colours - from lime green to antique pink to creamy white. There are many cultivars to grow with some staying extremely compact and only growing two to three feet tall and others maturing at a height of fifteen feet. My favourite is Limelight which produces massive flowers that start off lime green eventually maturing to a mix of white, pink, and burgundy. Little Lime is a dwarf version of Limelight that is perfect for small space gardens.
Smooth Hydrangea (Hydrangea arborescens)
There are several cultivars of smooth hydrangeas but Annabelle is by far the most common and most popular. These are hardy plants, down to zone three and form three-foot tall mounds of deep green heart-shaped leaves. In early to mid-summer the large pom-pom flowers emerge. The greenish-white flowers can last for six weeks, or longer if planted in a site with morning sun and mid-afternoon shade. Under tall deciduous trees is ideal. Annabelle makes a spectacular hedge along a pathway or at the back of the garden.
Oakleaf Hydrangea (Hydrangea quercifolia)
Oakleaf hydrangea is a North American native that grows six to eight feet tall and four to six feet wide. It flowers in mid to late summer but even when not in bloom provides plenty of garden interest. The leaves are deeply lobed, like oak leaves and turn a deep purple-red in autumn. In winter the exfoliating cinnamon-brown bark is visible. The flower clusters are very striking and form long cones packed with single or double white flowers. There is also a pinkish-red flowering cultivar called Ruby Slippers. Popular white flowering varieties include Snow Queen and Snowflake.
Climbing Hydrangea (Hydrangea petiolaris)
Climbing hydrangea is a true climbing plant that uses suckers to scale up walls, pergolas, and other structures. While it can take a few years from planting for the vine to begin climbing, once it’s settled in it grows quickly! Be sure to provide very sturdy support as the vine can grow up to fifty feet long. In mid summer the softly fragrant, lace-cap flowers appear. They’re a lovely creamy white and last for months. As the plant matures, the bark begins to exfoliate which adds winter interest to the garden.