What other tree can give you as much value in a public landscape, rural property or private garden as a blackwood? Acacia melanoxylon provides edible, ornamental, environmental and agricultural benefits to those people who choose to grow it. Could that be you?
Seen below is, not an eye, rather the seed of a blackwood (Acacia melanoxylon) around which is wrapped a reddish-coloured aril, a type of elaisome. Bet you didn't think you were getting a botany lesson today! Elaiosomes are nutrient-rich structures attached to the seeds of certain plants, including acacias, composed of lipids, proteins, and sugars and serves as an attractant. The aril on a blackwood seed entices birds to eat the seed, thus facilitating its dispersal to new locations through their droppings.
Whilst humans don't eat the aril, we can eat the seed after roasting. Blackwood seed can be harvested and roasted, and used in a variety of dishes after crushing and roasting. Rees Campbell outlines how to collect and cook this seed in her book, Eat More Wild Tasmanian. If you are interested in exploring this further, I highly recommend you get yourself a copy of this book or at least follow Rees on her Feisty Tasmanian page on Facebook. That is her area of expertise, not mine. I usually leave the cooking in our home to Ludovic, so that is all I will see on the edible aspects of acacia for the moment. However, I do have a couple of things to share about the use of this tree in the garden more generally. Firstly though, let's explore its distribution and growing requirements.
Acacia melanoxylon belongs to the Fabaceae (Legume/Pea/Bean family). The name melanoxylon means black wood, thus its common name – backwood. This species is sometimes referred to as Hickory, Sally Wattle and Mudgerabah on the Australian mainland. In Tasmania, the palawa kani word for this plant is rriyalimana (Campbell, 2022). Koories called it by various names, including Mootchung, and Burn-na-look.
Blackwood has a widespread distribution, from northern Queensland to southern Tasmania, and at altitudes from sea level to 1250-1500m. It is common from as far north as Atherton Tableland in Queensland, along the highlands of New South Wales and Victoria into Tasmania. It occurs again in Mt Lofty Ranges region of South Australia. In Victoria, it is found particularly in the Otway Ranges and Gippsland districts. However, the trees providing this timber grow best in Tasmania, where it occurs throughout native forests from sea level to 1000m in elevation but it really thrives in swamp and riverine areas.
If you are looking to grow blackwood, here is a summary of its usual growing conditions and environmental tolerances:
Rainfall - Grows in areas with a mean annual rainfall of between 705 – 1500mm. Very common on a variety of sites where annual rainfall exceeds 600mm (including basalt plains of Western Victoria).
Climate - Preferred conditions are sheltered sites in cool and warm humid climatic zones, with a high annual rainfall (900mm). It will grow in climates with a mean hottest month between 23-36°C, and the coldest month between 1-10°C, other conditions permitting of course. It will tolerate 1- 40 frosts a year.
Soil - On clayey and basalt soils. Grows well on fertile soils (krasnozems, acid brown earths, alluvial and brown loams), intermediate sites (red or yellow podzols and gley soils) and dry sites (red brown earths). For good results, a pH of 6-6.5 should be maintained.
In Tasmania, blackwood is a large erect tree growing up to 30 metres tall (Launceston Field Naturalists Club, 2019). However, it can grow up to 50 metres in height in the blackwood swamps of the north west, but is usally shorter in the understorey of wet eucaltypt forests and a shrub in drier habitats (Wiltshire & Jordan, 2018).
In large enough spaces, and in the right climate and soils, I like to include blackwoods in our landscape and garden designs. Once mature, and with a little uplifting of the lower branches, this species can make a very attractive evergreen shade tree. It has such a beautiful form.
Blackwoods are also reputed to be fire retardant plants, i.e. plants that will not burn in the first wave of a bushfire, but may burn once dried out (Marriott, n.d.). In our designs, I do not place blackwood in the Building Protection Zone (BPZ) immediately adjacent to the house, i.e. the defendable space in the event of a bushfire; rather in the Fuel Modified Zone (FMZ). This outer zone sits between the BPZ and unmanaged vegetation beyond the defendable space. Vegetation in this zone is managed to a more moderate level to substantially decrease the fround fuel and restrict the fuels available to an approaching bushfire.
In addition to slowing down bushfires, blackwood provides excellent value as a windbreak and shelter for animals. Unlike eucalypts, blackwood allows pasture growth up to its trunk and so is a preferred livestock shade tree by landowners. Blackwood is also used extensively in agroforestry. Its timber is highly prized as one of the best cabinet and furniture woods in the world. It lives in symbiosis with nitrogen-fixing bacteria Rhizobium and this, particularly in arid areas, substantially augments the soil nitrogen available for other plants of the community. And I have only just touched upon its habitat values and now aesthetic appeal! Consider its beautiful flowers which generally appear in late winter to the middle of spring (August to October) here in Tasmania and dark, leathery phyllodes, which are modified leaf stems fulfilling a similar function to leaves in regards to plant photosynthesis.
What's not to like about blackwood? If you have a rural property or a very large suburban block, I really would encourage you to grow one (or several), if your site conditions allow of course.
If you would like to know more about how you might include this magnificent plant in your garden or rural property, please reach out to me at gabrielle@inwardoutstudio.com. But for now, I will bid you goodnight ...
A bientot!
References
Campbell, R. (2022). Eat More Wild Tasmanian. Fullers Publishing.
Launceston Field Naturalists Club. (2019). A guide to flowers and plants of Tasmania. Reed New Holland Publishers.
Marriott, N. (n.d.). Fire resistant and retardant plants. Australian Plants Society (Victoria). Retrieved February 7, 2025, from https://apsvic.org.au/fire-resistant-and-retardant-plants/
Wiltshire, R. & Jordan, G. (2018). TreeFlip. University of Tasmania.
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