Species

Hydrangea macrophyllaBigleaf Hydrangea

60 other cultivars

shrub

Bigleaf Hydrangea

Hydrangea macrophylla 'Blue Cassell'

The Story

Plant Bio

Hydrangea macrophylla is a multi-stemmed deciduous shrub native to coastal Japan, grown for its broad serrated foliage and expansive summer bloom heads. The species displays either mophead or lacecap inflorescences whose sepal coloration converts based on soil pH and root absorption of aluminum.

'Blue Cassell' is a compact lacecap selection growing four to five feet tall with stiff, upright stems that support large flower heads without drooping. It features flat inflorescences of dark violet-blue sterile sepals in acidic soil and reblooms continuously from early summer into fall on both old and new wood.

Uses & Benefits:

Produces flat lacecap flower clusters with deep violet-blue sepals held on sturdy non-drooping stems.

Serves as a reliable reblooming mounded shrub suitable for shaded border midgrounds.

Provides opportunistic nectar sources for generalist native bees during summer.

SpeciesHydrangea macrophyllaBigleaf Hydrangea

Essentials

At a Glance

Plant Type

Shrub

Height

59"

Width

59"

Light

Full Sun, Partial Sun

Zones

5, 6, 7, 8, 9

Water

Medium to high

Humidity

Moderate

Lifespan

Perennial

Native To

East Asia (Japan)

Toxicity

Low toxicity if ingested; foliage may cause mild contact dermatitis

Bloom period

Early summer – Fall

In flower about 6 months of the year

Planting

How to Grow

Plant in rich, organic soil that receives bright morning sun and afternoon shade.
Water regularly to keep the root zone damp, ensuring soil drains freely to prevent root decay.
Drench the soil with aluminum sulfate in early spring to maintain rich blue flower tones in neutral soils.
Trim spent flower stems lightly right after the initial summer bloom flush without cutting into base framework.

Pro Tip

Apply aluminum sulfate in early spring before root uptake begins, as amending soil chemistry during flowering is too late to shift current-season blooms to deep blue.

Keep It Thriving

Care Guide

Do

Keep soil consistently moist throughout hot dry spells.
Provide shade protection from scorching afternoon sunlight.
Mulch root zones with organic material to retain moisture.

Don't

Do not cut structural old wood hard in late winter or early spring.
Do not allow soil to dry out completely during active blooming.
Do not over-apply high-nitrogen fertilizers that suppress flower bud development.

Seasonal Care Calendar

Task	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Fertilize
Mulch
Pest Check
Prune

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Cottage GardensMixed Shrub BordersContainer PlantingsCut Flower Gardens

Companion Plants

Hosta Heuchera Astilbe Athyrium filix-femina

Multiply

Propagation Methods

Good to Know

Common Questions

Bigleaf Hydrangea questions

What zones can Bigleaf Hydrangea grow in?

Bigleaf Hydrangea is hardy in USDA Zones 5–9. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

Is Bigleaf Hydrangea deer resistant?

Not reliably. Deer may browse Bigleaf Hydrangea, especially tender spring growth — plan on repellents or fencing where pressure is high.

When does Bigleaf Hydrangea bloom?

Bigleaf Hydrangea typically blooms in early summer through fall. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.

Does Bigleaf Hydrangea need full sun?

Bigleaf Hydrangea does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.