Hydrangeas have wonderful characteristics that make them a good focal point in almost any garden. They shine in a perennial border, they look elegant tucked in behind evergreen shrubs or they can stand alone in the landscape. Plus, you can plant several different varieties that will give you color from late May until late September.
In our garden, oakleaf hydrangeas are the first to bloom. They have dramatic white blooms and stunning leaves that resemble an oakleaf, hence the name. The white flowers radiate and are then followed by a kaleidoscope of leaf color in the fall. Most oakleaf hydrangeas grow to be quite large, between 6 to 10 feet in height. There are some smaller varieties available that are also good looking. These native hydrangeas will take the heat of the South and are also quite cold tolerate for more northern gardens. Plus, oakleaf hydrangeas will tolerate drier conditions than some of the other hydrangea species.
Hydrangea arborescens or smooth hydrangeas start to flower shortly after the oakleaf flowers open. They grow between 3 to 4 feet tall and are perfect for the smaller garden. “Annabelle” is the most popular of this species with their massive white snowball-like flowers. “Annabelle” flowers open chartreuse, turn white and end the season with a repeat of the chartreuse color. In recent years, pink varieties have been developed and are quite stunning.
Bigleaf (H. macrophylla) are the next group to flower. We have some varieties that start to bloom in early to mid June and others that do not open until mid July. Bigleaf hydrangeas are divided into two groups, which are based on the shape of the flower. Mopheads have round ball-shaped flowers and lacecaps have a more delicate flower with lovely sterile flowers around a cluster of fertile flowers. These hydrangeas are the most grown and used hydrangea and are the ones that come to mind when most people think of hydrangeas.
Bigleaf hydrangeas range in color from pink to purple to light blue or deep blue and white. When pigment is present, the bloom color can change with the pH of the soil. The flowers turn pink in limestone soil or when lime is added and turn blue with an acidic soil or when aluminum sulfate is added to the soil. The white flowers have no pigment and will remain white in either type of soil.
Bigleaf hydrangeas need very little pruning and should only be pruned immediately after they flower. Dead wood can be removed at any time, of course. If they do not bloom for a season, it tends to be one of the following reasons. A late frost comes in the spring; an early freeze comes in the fall; or the plant has been pruned too much or pruned too late in the season. They might also fail to bloom if they do not get enough sun or moisture.
Panicle hydrangeas (H. paniculata) follow the other hydrangeas and are laden with cone-shaped flowers. These plants bloom in a wide variety of climates, being quite cold hardy, growing in zone 3. However, they do not perform as well in the heat of the deep South.
Panicle hydrangeas are more tolerant of pruning. They can be pruned quite dramatically in the winter or very early spring. They bloom on new wood which is the reason they can take such intense pruning.
Panicle hydrangeas can range in size from about 3 to 8 feet tall and support flower clusters that emerge white and fade to pink, green or burgundy. The older varieties tend to grow quite tall while some of the newer varieties like “Little Lime,” “Bobo” and “Little Lamb” tend to be much shorter, ranging from 3 to 5 feet tall.
They traditionally have bloomed quite late in the summer. However, some of the newer varieties start blooming earlier than some of the older varieties. “Limelight” is probably the most noted paniculata and is extremely popular in the florist trade. Some of the varieties like “Limelight” have flowers that are quite full whereas “Tardiva” and “Brussels Lace” and others have more lace-like flowers that are quite dainty. “Pee Gee,” “Pinky Winky,” and “Pink Diamond” are other varieties that are easy to find. There are many new ones available that turn a lovely pink to burgundy as the flowers mature.
Hydrangeas are extremely vigorous, long-lived shrubs that brighten any garden or flower arrangement. As you can see, they come in a wide range of shapes and colors and are worth learning more about and growing. I hope you will find space for a few of these wonderful plants in your garden.
— Betty Montgomery, a master gardener and author of a “Four-Season Southern Garden,” can be reached at firstname.lastname@example.org.