How to Grow and Care for Annabelle Hydrangea

Annabelle hydrangea earns its reputation as one of the best-loved, smooth hydrangeas. This shrub (Hydrangea arborescens 'Annabelle') grows 3 to 5 feet tall with a 4- to 6-foot spread and is covered all summer in huge, rounded flowers measuring up to a foot across. Large, crisp white blooms make a statement against a background of dark green, sharply toothed foliage.

Annabelle hydrangea is a low-maintenance cultivar adapting to both soil type and sun exposure, as long as it's grown in moist, acidic soil. This shrub is also tolerant of black walnut. All hydrangeas are toxic when eaten to cats, dogs and horses.

Annabelle Hydrangea Care

Annabelle hydrangea is considered a low-maintenance shrub that grows well in clay and rocky soils with adequate moisture. This cultivar thrives in rain gardens, borders, and flower beds and is an outstanding choice for foundation plantings and woodland settings. It's native to the U.S., blooming reliably on new wood every growing season.

Light

Plant Annabelle hydrangea where it receives morning sun and afternoon shade. The shrub tolerates full sun only in locations that are consistently moist. It can survive in full shade, though blooms may be diminished without some sun exposure.

Soil

Soil acidity does not impact the color of this hydrangea's white flowers. Annabelle hydrangea adapts to soil composition from clay to sandy with pH levels of 5.5 to 6.5.

Water

Annabelle hydrangea is not drought tolerant, so it must be watered regularly throughout the growing season to keep soil consistently moist. The leaves and flowers decline in hot, dry conditions. In southern regions you may have to water as much as three times a week.

Temperature and Humidity

Temperatures between 65 and 85 degrees F. provide the ideal environment for Annabelle hydrangea. Flowers fade quickly in heat levels above 85 degrees F. The shrub tolerates winter temperatures down to 30 degrees F. For best flowering, it needs a 6- to 8-week period of temperatures around 40 degrees F.

Fertilizer

Fertilize Annabelle hydrangea annually in early summer with a slow-release, organic, acidic fertilizer with an NPK of 15-10-10 or 10-5-5. Alternatively, treat the leaves with kelp or fish emulsion foliar spray.

Pruning Annabelle Hydrangea

This cultivar blooms on new wood, which means the only time not to prune is when new spring growth emerges.

In autumn, you can remove the flowers, which have faded to tan, or leave them on for winter interest. They should be removed in late winter, along with any diseased or damaged branching. Annabelle hydrangea can also be cut to ground level in winter or when the growing season ends. Leave several old growth branches to support new growth and the large, heavy flowerheads.

Propagating Annabelle Hydrangea

Annabelle hydrangea is propagated with softwood cuttings taken in spring. You'll need 3- to 5-inch pots with drainage holes, sandy potting mix, rooting hormone, and sterile clippers. Here is how to increase your collection.

1. Fill several small pots or a larger pot with loose, sandy potting mix. Several cuttings can be rooted in one larger pot.
2. Clip 6 to 12 inches of a new branch that has five or six softwood stems and leaves.
3. Separate softwood stems from the main branch and remove lower leaves from these cuttings.
4. Dip the bottom of each cutting in rooting hormone to cover the nodes where bottom leaves were removed.
5. Make deep, narrow holes in the potting mix and insert bottoms of the cuttings into the holes. Three to four cuttings can be placed in a 5-inch pot.
6. Water and continue to keep soil moist.
7. Place in a shaded area with filtered or indirect light. Roots form in two to three weeks.
8. Pot up individual seedlings into their own 3- to 5-inch containers and grow out until fall when new shrubs can be transplanted into the garden.

Overwintering

Because Annabelle hydrangea blooms on new growth, only its roots need protection for winter temperatures that dip below 30 degrees F. Maintain a 3-inch layer of wood chips or pine straw and add more in fall in needed. Mulch will also help retain soil moisture.

Common Pest and Plant Diseases

This smooth hydrangea is vulnerable to the larval form of the leaftier moth, which cocoons in leaves and can cause diminished flowering. When you find distorted foliage or leaves stuck together, this small, black-headed caterpillar is likely responsible. Organic pesticide BTK is effective as a preventive if applied on new leaves in spring. If caterpillars have established cocoons, remove and dispose of the leaves and any damaged flower buds.

Leaf spot, powdery mildew, and rust aren't common but can affect Annabelle hydrangea. These are fungal infections that can usually be managed with proper moisture and sunlight exposure. In severe cases, spray foliage with the recommended fungicide.

How to Get Annabelle Hydrangea to Bloom

Colossal, clean white blooms are Annabelle hydrangea's main attraction, along with reliably extended bloom periods when adequate growing conditions are provided.

Bloom Months

Annabelle hydrangea first blooms in June as small green corymbs (flower clusters) that open to white as they increase in size. Blooming continues through August with a brief re-blooming phase in autumn.

What Do Annabelle Hydrangea's Flowers Look and Smell Like?

Annabelle hydrangea has 12-inch clusters of dozens of small white flowers that cover the shrub in prolific numbers. Flower heads are uniform and rounded, resembling large snowballs. Buds are green but turn white when fully open and hold color until autumn when they fade to tan. Annabelle hydrangea's flowers aren't fragrant.

Deadheading Annabelle Hydrangea Flowers

It's not necessary to deadhead Annabelle hydrangea. They can be cut for fresh flower arrangements or preserved for dried bouquets. Annabelle hydrangea is often pruned back to ground level following autumn bloom, with faded flowers removed at the same time.

Common Problems With Annabelle Hydrangea

This smooth hydrangea cultivar is relatively problem free. Regular watering to keep soil consistently moist, planting in well-draining soil, and pruning back to ground level in autumn work to avoid fungal infections and insect pests that plague other ornamental shrubs.