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Smooth Hydrangea

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Facts About Smooth Hydrangeas

Native to the southwestern United States, smooth hydrangea (Hydrangea arborescens) is an exceptionally hardy deciduous shrub that is cherished for its large globe-shaped flowers and no-fuss upkeep once established. Most smooth hydrangea flowerheads bloom greenish-white in the summer and gradually switch to white before taking on a buttery-yellow shade in the fall.

When planting, pay close attention to the variety. Not long ago, smooth hydrangea was almost exclusively over 5 feet tall and 5 feet wide and could reach up to 10 feet in both directions. However, new varieties that are as small as 2 feet by 2 feet are now available.

There are four main types of hydrangeas in the United States: Bigleaf, Panicle, Oakleaf, and Smooth. Each type is fantastic in its own way and worth exploring. Check out our complete guide to hydrangeas to learn which type of hydrangea is right for your garden.

Smooth Hydrangea Growth and Care

Smooth hydrangea are easy to please as long as you follow a few simple instructions. Once they’re established, you can sit back and enjoy their grandeur.

Temperature and humidity: Smooth hydrangeas are more heat and cold-tolerant than other hydrangea varieties, making them adaptable to a range of climate conditions. They’re hardy in USDA zones 3 through 9. If you love Bigleaf hydrangeas but live in a colder climate, smooth hydrangeas are a great alternative.

Where to plant: Wind damage can prevent smooth hydrangea from blooming. Protect your plant with windbreakers, such as trees or other plants.

When to plant: Plant your smooth hydrangeas in mild weather during the spring and fall. 

How to plant:

  1. Dig a hole twice the width and slightly deeper than the root ball. 
  2. Remove the plant from its container and loosen the soil around the roots.
  3. Place the shrub in the hole so it is level with the ground, and cover it with soil. Gently pat down to release air pockets. 
  4. Water regularly until the shrub is established.

Smooth hydrangeas grow best in partial shade but can do well in full sun. To reach maximum bloom, they require 4 to 6 hours of direct sunlight per day. If you live in the South, your hydrangeas will need shade from the blazing sun in the afternoon. 

Soil: Smooth hydrangeas are easy to please. They tolerate poor soil conditions as long as the area drains well and the shrub is kept moist. They prefer neutral to slightly acidic soil with a pH between 6.0 and 7.5. Also note that, unlike Big Leaf hydrangea, the bloom color of smooth hydrangea cannot be altered by changing the soil's pH level.

Water: Hydrangea arborescens thrive with regular water but don’t water log the soil. Water your plant more frequently during dry spells and prolonged heat. Smooth hydrangeas in containers need more water than ground plants.

Fertilizer: In early spring, feed your smooth hydrangea a balanced, all-purpose fertilizer to promote growth. Be careful not to over-fertilize, which can cause leaf burn and yellow foliage. Also, avoid nitrogen-rich fertilizer, as it encourages foliage growth instead of blooms.

Mulch: Apply a 2-inch layer of mulch around the base of the plant to retain moisture and prevent weeds. 

Pruning: Smooth hydrangeas bloom on new wood (unlike most hydrangea varieties), so it’s best to cut them back in the early spring before new growth starts. We recommend cutting back to about one foot from the ground. You can remove about one-third of the plant without damaging it. 

Common problems: Smooth hydrangea are tough. When grown in the right conditions, they won’t have serious issues. However, watch for common hydrangea pests such as aphids, Japanese beetles, scale, and spider mites. 

Powdery mildew, a common fungal disease, can also be an issue because the plant prefers moist, humid conditions. To avoid the fungus, avoid overwatering and crowding. Prune to promote air circulation. If you spot powdery mildew, which has a white to grayish color, pick off the infected leaves and trim shoots. 

Animals: Smooth hydrangea is playfully known as “deer candy” among our experts. Deer love to eat this plant's flower buds and foliage. If deer are common in your area, protect your smooth hydrangea with a physical barrier or a spray. You might also consider planting a more deer-resistant hydrangea like Bigleaf hydrangea. 

Toxicity: Like most hydrangea, smooth hydrangea is toxic to people and pets if ingested. The plant contains cyanogenic glycosides, which can cause vomiting, diarrhea, and lethargy.  

Age: Smooth hydrangea can live about 20 years under ideal conditions.

Varieties of Smooth Hydrangea

New varieties of  hydrangea smooth leaf are popping up everywhere, mostly thanks to the efforts of researchers at ​​North Carolina State University. We’ve highlighted three smooth hydrangea varieties and why home gardeners adore them.  

Annabelle Hydrangea Shrub: The most popular of smooth hydrangeas, the Annabelle variety is known for its massive greenish-to-white flowerheads, which can reach up to 12 inches across, and its ability to rebloom late in the season. Its fluffy blooms are a favorite of cottage gardens. It’s also perfect for planting in mass along borders. 

Hardiness: USDA zones 5 to 9
Size: 3-5 feet tall x 3-5 feet wide
Growth rate: Fast
Sunlight: Full sun to partial shade
What makes Alice Hydrangea unique:
Huge, dazzling white blooms.
A second bloom late in the season.

    Bring stunning white blooms to your garden today. See Annabelle Smooth Hydrangea for sale.

    The Annabelle Hydrangea is the most popular smooth hydrangea variety. 

    The Annabelle Hydrangea is the most popular smooth hydrangea variety. 

    Haas Halo Hydrangea Shrub: This smooth hydrangea is a hit among home gardeners and pollinators alike thanks to its white lace cape flowers, which can bloom up to 14 inches wide, and leathery blue-green foliage. It makes a show-stopping specimen plant and a breathtaking addition to a habitat garden. 

    Hardiness: USDA zones 3 to 8
    Size: 3-5 feet tall x 3-5 feet wide
    Growth rate: Fast
    Sunlight: Full sun to partial shade
    What makes Alice Hydrangea unique:

    Unmatched pollinator.
    Brilliant, extra large flowers.

    Incrediball Hydrangea Shrub: A standout among smooth hydrangea, Incrediballs possess more flowers than other varieties and stronger stems that keep the plant from sagging. Like other hydrangea, it’s perfect for hedges, screens, and woodland edges. 

    Hardiness:USDA zones 3 to 9
    Size: 4-5 feet tall x 4-5 feet wide
    Growth rate:Moderate
    Sunlight: Full sun to partial shade

    What makes Alice Hydrangea unique:
    More showy white flowers.
    Sturdy, strong stems.

    The Incrediball is another popular variety of smooth hydrangea.

    The Incrediball is another popular variety of smooth hydrangea.

    Benefits of Smooth Hydrangea

    Easy to grow: Smooth hydrangeas are the perfect mix of strength and beauty. They are heat and cold tolerant, grow in poor soil, require little maintenance, and have no significant pest or disease issues.

    Large, showy flowers: The shrub’s large, globe-like blooms—which range from white to pink, depending on the variety—make a stunning statement. But color isn’t the only reason this shrub is popular. Smooth hydrangea flowerheads can reach a jaw-dropping 14 inches wide. 

    Versatility: While hydrangea arborescens’ flowerheads might be large, overall, it’s a compact shrub that will work well in most spaces. It can be used as a specimen plant or as an eye-catching hedge along a boundary line, fence, or driveway. It’s also an excellent choice for wildlife gardens and will attract bees and butterflies. Like all hydrangea, smooth hydrangea spreads through suckering roots, making it a fantastic option for erosion control.

    Turn your garden into the talk of the neighborhood with smooth leaf hydrangea today.

    Common Questions About Smooth Hydrangeas

    Are smooth hydrangeas poisonous?

    Smooth hydrangeas should not be ingenious and can be toxic for dogs, cats, horses, and other wildlife. 

    Should you deadhead smooth hydrangeas?

    You should deadhead smooth hydrangeas throughout the blooming season to promote healthy growth. Learn more about deadheading in our guide

    More Smooth Hydrangeas Resources

    Types of Hydrangeas: Which Hydrangea Should You Plant?

    Mini Makeover: Kristen's Hydrangea Corner

    Caring for Hydrangeas: Our Top 4 Tips for Success