shrub

Harkness bottlebrush

The Story

Plant Bio

Callistemon is a genus of evergreen Australian shrubs and trees characterised by woody seed capsules and dense, cylindrical flower spikes dominated by long, colourful stamens. These plants are highly adapted to fire and seasonal moisture fluctuations, often growing naturally along watercourses or in damp depressions.

'Harkness' is a vigorous hybrid of *Callistemon viminalis* and *Callistemon citrinus* that forms a large, dense shrub or small tree with weeping branchlets and bronze-red new growth. It produces exceptionally long, crimson-red flower spikes up to 15 centimetres in length during spring and summer.

Uses & Benefits:

Produces long, dense, crimson-red flower spikes and striking bronze-red new growth on a weeping form.

Provides a resilient, drought-tolerant screen or windbreak suitable for second-line coastal exposure.

Highly attractive to Australian nectar-eating birds, native bees, butterflies, and beneficial insects.

Essentials

At a Glance

Plant Type

Shrub

Height

236 inches

Width

157 inches

Light

Full Sun, Partial Sun

Zones

9, 10

Water

Low to moderate

Humidity

Moderate

Lifespan

Long-lived

Native To

Australia (Garden origin)

Toxicity

Non-toxic

Bloom period

Spring – Summer

In flower about 4 months of the year

Planting

How to Grow

Plant in a full sun position to maximise flowering, though light shade is tolerated.
Water regularly during the first growing season to establish a deep, resilient root system.
Apply a low-phosphorus or native-safe fertiliser in spring to support vigorous new growth.
Prune lightly to moderately right after flowering to maintain a dense, compact habit.

Pro Tip

Prune immediately after flowering to maintain a dense habit; cutting back hard into bare, brown wood will prevent the plant from shooting back.

Keep It Thriving

Care Guide

Do

Prune immediately after the main flowering flush to encourage new growth.
Water deeply during extended dry periods to prevent the plant from becoming woody.
Check young foliage regularly for signs of myrtle rust.

Don't

Do not cut back hard into old, leafless brown wood.
Do not plant close to underground sewer lines or pipes.
Do not use overhead watering, which can encourage fungal diseases like myrtle rust.

Seasonal Care Calendar

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

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Second-line coastal plantingsScreening and informal hedgingSpecimen planting

Multiply

Propagation Methods

Good to Know

Common Questions

Harkness bottlebrush questions

What zones can Harkness bottlebrush grow in?

Harkness bottlebrush is hardy in USDA Zones 9–10. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

When does Harkness bottlebrush bloom?

Harkness bottlebrush typically blooms in spring through summer. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.

Does Harkness bottlebrush need full sun?

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

Is Harkness bottlebrush drought tolerant?

Yes — once established (usually after the first full season), Harkness bottlebrush handles dry spells with minimal watering. Water deeply its first year to build the root system that makes that possible.