Annabelle hydrangea

Sun

Partial shade, ideally morning sun and afternoon shade. Full sun works in cooler climates if the soil stays moist; avoid harsh afternoon sun in hot regions.

Water

Keep the root zone evenly moist, especially during establishment and hot weather. Water deeply during dry spells; avoid waterlogged soil.

Soil

Humus-rich, moist but well-drained soil. Tolerates clay if drainage is adequate and grows in acidic to mildly alkaline soil; soil pH does not turn the flowers blue or pink.

Height

3-5 ft (0.9-1.5 m)

Spread

3-5 ft (0.9-1.5 m), gradually wider through suckering

Flowers

Early to late summer: rounded heads of mostly sterile flowers open pale green, turn white, then fade to green and tan. Dried heads can persist into winter.

Foliage

Broad, oval, medium-green leaves with toothed edges; autumn colour is usually unremarkable yellow-green.

Growth

Fast once established.

Care needed

Medium

• Cold hardy
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1.6 ft (0.5 m)

2. After 1 year

   2.3 ft (0.72 m)

3. After 2 years

   3 ft (0.93 m)

4. After 3 years

   4 ft (1.1 m)

5. After 5 years

   4 ft (1.2 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Native to

the US

Growth rate

Fast

• Water deeply when the soil starts to dry; do not rely on brief surface watering.
• Apply 2-3 in (5-8 cm) of organic mulch each spring, keeping it clear of the stems.
• Top-dress with compost in spring; use a modest amount of balanced fertiliser only if growth is weak.
• Fit a discreet support ring before shoots become tall, especially in exposed sites.
• Remove unwanted suckers at the edge of the clump to control its spread.

Pruning. In late winter or early spring, remove dead and weak stems and shorten the remaining stems to a sturdy framework about 18-24 in (45-60 cm) tall. Avoid cutting everything to ground level each year if flopping is a problem; retaining older stems can provide support.

Late winter

Leave dried flower heads for winter interest, then remove them as you begin pruning before spring growth.

Early spring

Prune out dead and weak stems, top-dress with compost and renew the mulch.

Mid-spring

Install supports before the new shoots become tall.

Early summer

Take softwood cuttings from healthy, non-flowering shoots.

Summer

Check soil moisture during dry weather and water deeply when needed.

Autumn

Plant while the soil is workable, water thoroughly and remove unwanted rooted suckers.

• Plant in groups along a partly shaded boundary for a broad band of white summer flowers.
• Combine with hostas and ferns at a woodland edge for contrasting leaf shapes.
• Use as an informal low hedge beside a lawn or path, allowing room for arching stems.
• Pair with dark evergreen shrubs in a white garden so the flower heads stand out.

Garden styles it suits: English country, Cottage garden, Woodland, White garden, Traditional and Romantic rose garden.

Plant it with: Hostas, Astilbes, Japanese painted ferns, Coral bells, Solomon's seal and Siberian bugloss.

Wildlife: The dense flower heads contain mostly sterile florets, so they provide little food for pollinators compared with fertile-flowered smooth hydrangeas. The shrub offers some shelter for small garden animals; deer may browse it.

• Flopping stems: fit supports early, shelter from strong wind and avoid excessive nitrogen or annual ground-level pruning.
• Wilting or scorched leaves: check soil moisture, water deeply and provide afternoon shade in hot climates.
• Powdery mildew: improve air circulation, avoid overcrowding and keep roots evenly moist.
• Leaf spots: remove fallen affected leaves and water at soil level; minor spotting usually needs no chemical treatment.

Toxic if eaten by cats, dogs, horses or people. Leaves, buds and other parts contain cyanogenic compounds; ingestion most often causes vomiting, diarrhoea or abdominal discomfort, while serious poisoning is uncommon but possible after substantial ingestion. Keep prunings away from pets and livestock, and seek medical or veterinary advice if eaten.

• Mophead hydrangea (Hydrangea macrophylla)

  Usually has thicker, glossier leaves and sturdier stems. Many cultivars have pink or blue flowers, though white forms also occur; many flower mainly on older wood.

• Panicle hydrangea (Hydrangea paniculata)

  Has cone-shaped rather than rounded flower heads, usually on a more upright, woody framework; many cultivars turn pink as the flowers age.

• Snowball viburnum (Viburnum opulus 'Roseum')

  Has distinctly three-lobed, maple-like leaves and rounded white flower clusters in spring rather than summer.

The cultivar name 'Annabelle' refers to Anna, Illinois, where the original plant was found.

Propagation. Take softwood cuttings in early summer, or separate well-rooted suckers in spring or autumn. Vegetative propagation preserves the cultivar; seedlings will not reliably match it.

Accepted botanical name

Hydrangea arborescens

In the US and Canada

Native in the lower 48 states. Introduced in Canada.

Native range

Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Maryland and Mississippi.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.