Incrediball smooth hydrangea

Sun

Full sun to partial shade; morning sun and afternoon shade are best in hot climates. Full sun works well in cooler regions if the soil stays moist.

Water

Keep evenly moist, especially during establishment and hot weather; avoid waterlogged soil. Large leaves wilt readily when the roots become dry.

Soil

Moist, well-drained soil enriched with organic matter. Tolerates clay if drainage is adequate; flower colour does not turn blue or pink with changes in soil pH.

Height

4-5 ft (1.2-1.5 m)

Spread

4-5 ft (1.2-1.5 m)

Flowers

Summer into early autumn; rounded heads open pale green, become white, then age to green and eventually tan.

Foliage

Broad, pointed, toothed green leaves; deciduous, with usually modest yellow autumn colour.

Growth

Fast once established.

Care needed

Low

• Cold hardy
• Wildlife
• 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

   2.5 ft (0.76 m)

3. After 2 years

   3 ft (1 m)

4. After 3 years

   4 ft (1.3 m)

5. After 5 years

   4 ft (1.4 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 upper soil begins to dry; check new plants frequently through their first growing season.
• Apply 2-3 in (5-8 cm) of organic mulch, keeping it clear of the stem bases.
• Top-dress with compost in spring; use a balanced shrub fertiliser only if growth is weak or soil fertility is low.
• Provide afternoon shade in hot regions and shelter from drying winds.
• If rain-heavy flower heads lean, use a discreet support early in the growing season rather than tying stems tightly.

Pruning. In late winter or early spring, remove dead and weak stems and shorten the remaining stems by about one-third. Avoid cutting every stem to ground level each year if you want a stronger framework to support the large flower heads.

Late winter

Leave sound stems standing until pruning time; remove any broken branches.

Early spring

Prune before strong new growth begins, retaining a sturdy framework.

Spring

Plant when soil is workable, water thoroughly, and refresh the mulch.

Late spring

Check soil moisture as growth accelerates and install supports if needed.

Summer

Water deeply during dry spells and check leaves for mildew or spotting.

Autumn

Leave fading flower heads for structure, or remove them if you prefer a tidier appearance.

• Plant in groups along a partly shaded border for a broad band of white summer flowers.
• Use as an informal flowering hedge, allowing enough width for its mature spread.
• Combine with ferns and hostas at a bright woodland edge for contrasting leaf shapes.
• Set against dark evergreen shrubs to make the white flower heads stand out.
• Use in a white garden with shade-tolerant perennials and spring bulbs.

Garden styles it suits: English country, Cottage garden, Woodland, White garden, Traditional and Low-maintenance.

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

Wildlife: The showy flower heads are dominated by sterile florets and offer much less food for pollinating insects than lacecap smooth hydrangeas. The branching shrub can provide cover for small garden wildlife.

• Wilting or scorched leaf edges: check soil moisture, water deeply if dry, and provide afternoon shade in hot locations.
• Powdery mildew: improve air circulation, avoid crowding, and keep the roots evenly moist.
• Leaf spots: remove fallen affected leaves and water at soil level rather than wetting the foliage.
• Leaning or flopping flower stems after rain: retain a woody framework when pruning, avoid excessive nitrogen, and add discreet supports if necessary.

Toxic to cats, dogs, horses and people if eaten. All parts contain cyanogenic compounds, with leaves and flower buds a particular concern. Ingestion commonly causes digestive upset; serious poisoning is uncommon but possible, especially if a large amount is eaten. Keep prunings away from pets and livestock.

• Annabelle smooth hydrangea (Hydrangea arborescens 'Annabelle')

  Very similar, but its stems generally bend more readily under the flower heads. Incrediball was selected for stronger stems and large heads; a label is the most reliable way to distinguish young plants.

• Bigleaf hydrangea (Hydrangea macrophylla)

  Usually has thicker, glossier leaves and often pink or blue mophead flowers. Smooth hydrangea has thinner, less glossy leaves, and Incrediball flowers remain white to green regardless of soil pH.

• Panicle hydrangea (Hydrangea paniculata)

  Has tapered, cone-shaped flower clusters rather than rounded heads; many cultivars develop pink tones as their flowers age.

Hydrangea comes from Greek words meaning water vessel, referring to the seed capsules, while arborescens means becoming tree-like.

Propagation. Softwood cuttings taken in late spring or early summer can produce plants true to the cultivar; seedlings will not reliably match it. This is a protected cultivar in some countries, so check current local propagation rights before taking cuttings.

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.