Hydrangea Care Guide: How to Grow Hydrangeas

Also commonly called hortensia, hydrangeas make up a genus of more than 75 species of flowering shrubs. The name “hydrangea” is derived from the Greek word hydria, meaning “water vessel.” Although widely grown in the American Southeast, these plants are native to both Asia and North America. They can be either deciduous or evergreen and grow as climbing vines, trees, or––most commonly––shrubs.

Known for their beautiful blooms and soft, leafy foliage, hydrangeas range in size from one-foot-tall shrubs to 100-foot climbing vines. The size, shape, and color of hydrangeas vary among species:

1. Bigleaf hydrangeas (Hydrangea macrophylla): These hydrangeas have two flower types: mopheads, which are notable for their large globe-shaped flower heads, and lacecaps, which have flattened heads of small flowers surrounded by a ring of large flowers. The coloring of Hydrangea macrophylla flowers depends on soil type. Bigleaf hydrangeas bloom on old wood in the spring, and they thrive in shade.
2. Smooth hydrangeas (H. arborescens): Smooth hydrangeas do well in spaces that receive morning sun and afternoon shade and require consistently moist soil. Fertilize them in late winter. They bloom in the summer with flower colors that range from white to pink. Other than their smoothly textured leaves and shorter height, the Hydrangea arborescens is similar in appearance to bigleaf hydrangea shrubs.
3. Panicle hydrangeas (H. paniculata): Panicle hydrangeas bloom in late summer and do well in colder climates. If you do not prune them, these deciduous hydrangeas can grow up to 15 feet tall. The Hydrangea paniculata thrives in direct sunlight and forms cone-shaped flower heads. Cultivars include Grandiflora, Tardiva, White Moth, and Limelight.
4. Oakleaf hydrangeas (H. quercifolia): Oakleaf hydrangeas flourish in full sunlight and grow in the woodlands of America’s Southeast. Their color ranges from white to purple, and their large, lobed leaves are similar in appearance to oak leaves. They generally bloom early spring to mid-summer.
5. Climbing hydrangeas (H. anomala petiolaris): These are vine plants that can grow up to 50 feet long or sprawl across 200 square feet of earth if grown without a structure to climb. They do well in part- to full-shade environments and their white flowers bloom in early summer.
6. Mountain hydrangeas (H. serrata): Mountain hydrangeas bloom pink or blue flowers from June to August. They are similar in appearance to lacecap bigleaf hydrangeas, though their leaves and flowers are smaller. They grow best in part shade and range in height from two to five feet.

Within the six species of hydrangeas are numerous varieties, which provide nearly endless possibilities for sprucing up your garden.

1. Limelight hydrangeas: Popular for its pale green flowers that bloom on new growth, the Limelight hydrangea is a great choice for colder environments. It grows relatively quickly and can reach up to 10 feet in height.
2. Cityline Mars hydrangea: The Cityline Mars is a bigleaf hydrangea featuring flowers with bold colors and patterns that are dependent on the pH of the soil in which it grows. It is native to Japan and grows one to three feet, and does best in direct sunlight.
3. Nikko Blue hydrangea: A mophead hydrangea, the Nikko Blue is native to Japan and thrives in partial shade. The vibrancy of its shade of blue depends on whether or not it is planted in acidic soil, and it ranges in height from four to six feet.
4. Incrediball hydrangea: The flowers of Incrediball hydrangea bloom in white, densely packed clusters that are supported on sturdy stems. They are native to the eastern United States and thrive in bright sunlight.
5. Zinfin Doll hydrangea: Known for attracting butterflies, this native of China and Japan grows best in full sun. Its flowers are mophead in shape and range in color from white to pink.
6. Gatsby Pink hydrangea: The Gatsby Pink prefers warm environments with partial shade. Its unusually shaped flowers bloom in white before cycling to pink, and it can grow as tall as eight feet.
7. Annabelle hydrangea: The deciduous Annabelle hydrangea is notable for its large, pure white flowers that can grow up to 12 inches across. It blooms in late spring to summer and often continues into the fall.
8. Invincibelle hydrangea: The Invincibelle is a smooth-leaf hydrangea that is valued for its hardiness. Its flowers are large––though not as large as the Annabelle hydrangea––pink, and bloom on new wood in the summer and fall.

Hydrangeas are adaptable plants that can grow in a variety of conditions. There are five considerations to keep in mind when caring for hydrangeas, especially when the plants are still young:

• Plant hydrangeas at the optimal time. Hydrangeas should be planted in fertile soil after the last spring frost or before the first fall frost. It’s best to plant them in the early morning or late afternoon, avoiding the hottest part of the day.
• Plant hydrangeas at least four feet apart. To plant a hydrangea, make sure you dig a hole that is at least as deep as the plant’s root ball and approximately twice as wide.
• Pick a shady plot of land. Generally, hydrangeas prefer at least partial shade, though there are some that prefer full, direct sunlight. Bigleaf hydrangeas, which are the most popular type, are prone to wilting, so ensure when planting that they will have some shade from the sun. If you are unable to provide partial shade to your hydrangea, slightly increase the amount of water you provide each week.
• Amend your soil to alter hydrangea flower colors. The type of soil you choose will affect the coloring of some types of hydrangeas, including H. macrophylla and H. serrata cultivars. When aluminum is available in soil, it means the soil is acidic, which will result in blue hydrangea flowers. When aluminum is unavailable, it is alkaline soil, which gives the hydrangea pink flowers. If you want your plant’s flowers to bloom pink, you can add hydrated lime to your soil. Adding aluminum sulfate will give your plant blue flowers.
• Water consistently. Give your hydrangeas one inch of water per week. While all varieties of hydrangea will thrive with consistent watering, bigleaf and smooth hydrangeas require the most. To prevent wilting, be sure to water your plants in the morning.

Hydrangeas do not pose a significant health hazard, but it is important to note that hydrangeas are technically poisonous plants. Glycoside amygdalin is contained in hydrangeas and has the potential to make them poisonous because it can produce cyanide. Hydrangea poisoning will only occur if a significant amount of leaves or flower buds are consumed. While it is highly unlikely that poisoning will occur, be cautious of where you plant your hydrangeas if you have pets or small children.

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