| Botanic name | Acacia melanoxylon |
| Other names | Blackwood |
| Main Origin | Eastern to southeastern Australia |
| Mature size | 2 – 8 m x 3 – 30 m (w x h) |
| Mature form | Shrub or upright tree with a dense canopy |
| Foliage | Narrowly elliptical, spear-shaped, glossy, dark green |
| Growth rate | Fast |
| Position | Full sun, part shade |
| Soil | Prefers deep, fertile soils, but adapts to other soils |
| Water | Regular deep watering during extended dry periods |
| Climate | Mediterranean, temperate, subtropical, tropical |
| Flower | Cream-white, spring and summer |
| Use | Feature specimen, screen, windbreak, avenue planting |
| Notes | Long-lived Acacia species |
Origin and distribution
Acacia melanoxylon, commonly known as Blackwood, is a superb all-rounder in natural and cultivated landscapes. Renowned for its lush green foliage, versatile form, and long life, it is widely planted in residential gardens, public parks and streetscapes.
The species is native to eastern and southeastern Australia. It mainly occurs along the coast or nearby areas and spreads further inland, particularly in southeastern Australia, where the climate is more temperate.
Its habitats range from wet, cool rainforests in mountains, valleys, or wetlands to drier and warmer inland areas associated with rivers, creeks, and hills. The species can often be spotted near farmlands and roadsides in higher rainfall regions.
Outside its natural range, Blackwood has become naturalised in temperate regions of southwestern Western Australia. The widespread overseas cultivation has led to its naturalisation in other countries, such as New Zealand and South Africa, where the species has become invasive.
Growth and care
Acacia melanoxylon thrives in regions with moderate to high rainfall, where temperate to cool climates dominate. However, it adapts to drier Mediterranean and more humid subtropical and mild tropical zones.
The species naturally grows in a range of soils. However, it thrives best in deep, nutrient-rich, and moist soils that are well-drained, slightly acidic to neutral, although it can tolerate alkaline, heavy or poor soils.
Blackwood can be dramatically different in size depending on climate, soil fertility, and water availability. Its growth preference is akin to Lilly Pilly. It can grow into a towering giant in sheltered wetlands and rainforests, but often appears much smaller or shrubby in more exposed, drier regions.
Although this species loves moisture and is highly tolerant of wet conditions and periodic waterlogging, it will not last in stagnant waterlogged sites.
On the other hand, Blackwood is highly tolerant of dry conditions once established, but prolonged drought conditions can lead to stunted growth, sparse foliage and overall decline in vigour.
Established Acacia melanoxylon is considered frost-hardy and can tolerate low temperatures to -7°C. Young seedlings are susceptible to frost damage and require protection in cold months. It is not an alpine species and does not tolerate prolonged freezing conditions.
Tips to support the healthy growth of Blackwood:
- Add organic matter when planting: Incorporate aged manure, compost, or other organic content, such as leaf mulch or worm castings, to improve soil structure and bioactivity.
- Mulch generously: Apply a thick layer of mulch around the base to retain moisture, suppress weeds, and improve soil health.
- Fertilise moderately: Blackwood prefers fertile conditions, unlike most Acacia species. Apply a slow-release, balanced fertiliser or compost to support steady, healthy growth during the growing season.
- Avoid waterlogging: The plant can tolerate wetness, but cannot survive sustained waterlogging. Avoid planting in highly compacted, heavy soils.
- Provide adequate moisture: Younger plants require regular deep watering, especially during prolonged dry spells.
Features
Acacia melanoxylon is a striking and highly versatile tree, known for its rich green foliage and sturdy, elegant trunk rising above the ground, even though the tree often appears somewhat stout due to the large portion of foliage coverage.
The straight trunk is often covered with smooth grey to dark brown bark that becomes rougher with age. The branches are well spaced, forming a balanced, rounded canopy that provides excellent shade.
The standout feature of Acacia melanoxylon is its lush, evergreen foliage that forms a deep green, rich canopy that adds a calming, natural beauty to the landscape.
In cultivation, it can reach 8 – 15 metres in height, depending on the growing conditions. It is highly versatile in landscaping, often maintained as a large shrub for effective screening, featuring gnarly branches in drier regions.
Whether planted in expansive landscapes or integrated into larger waterwise gardens, it contributes a graceful presence with year-round visual appeal.
The plant produces small, pale yellow or cream spherical, honey-scented blossoms that attract pollinators from spring to summer. Curved, brown seedpods follow.
With a fast growth rate, Acacia melanoxylon is widely used as a shade tree, windbreak, and timber production. It is a key species with significant ecological value. Like many other acacias, it is a nitrogen fixer and a prolific seeder, ideal for revegetation projects.
The species is known for its long lifespan compared to many other wattles. Under ideal conditions, it can live for 50 to 100 years or more, while it lives up to 25 – 50 years in less favourable, harsher conditions.
FAQs
Is Acacia melanoxylon fast-growing?
Yes. Acacia melanoxylon (Blackwood) is a fast-growing tree, especially in its early years. Under optimal conditions – such as fertile, well-drained soils and adequate moisture – it can grow 1 to 2 metres per year.
Is Acacia melanoxylon invasive?
Acacia melanoxylon (Blackwood) is not typically invasive in its native range of southeastern Australia, where it plays an important ecological role. However, outside its native range, it has shown invasive tendencies in several regions, due to its abilities to sucker from roots and produce seeds profusely.
The species has escaped cultivation and spread into natural areas in many countries. It can form dense stands, outcompete local vegetation, and alter soil chemistry through its nitrogen-fixing ability, leading to concerns about its impact on native biodiversity.
Because of this, it is classified as an environmental weed or invasive species in some regions, and planting may be discouraged or regulated. Careful consideration should be given when introducing it to non-native environments, particularly those with vulnerable ecosystems.
What kind of soil does Acacia Melanoxylon like?
Acacia melanoxylon (Blackwood) thrives best in deep, fertile, well-drained soils. It prefers loamy or sandy loam soils rich in organic matter, but it is also quite adaptable, growing in other soil types, including clay soils, as long as drainage is good.
While it can tolerate poor soils thanks to its nitrogen-fixing ability, it performs significantly better in nutrient-rich soils where it can develop faster, grow taller, and produce denser foliage. It prefers slightly acidic to neutral pH but tolerates mildly alkaline conditions.
What is Acacia Melanoxylon bark like?
Acacia melanoxylon (Blackwood) has distinctive light to dark grey to brown bark that becomes more furrowed and fibrous as the tree matures.
The bark of younger trees tends to be smoother and more finely textured, while on older trunks, it thickens and develops a deeply fissured appearance, giving the tree a sturdy, weathered look.
