Port Jackson

1. PORT JACKSON – Acacia saligna

YOUNG PORT JACKSON – Acacia saligna (Photo by Steve Coe)

A native of south-western Australia, the Port Jackson is a member of the Legume family, Fabaceae . It is an evergreen with a willowy appearance and has flattened, leathery, deep green, mainly drooping leaves, which are more upright and broader in the immature plants. It can grow into a tree, up to 9 meters tall and spreads prolifically, growing in dense thickets. It was originally deliberately imported and planted to stabilize sand dunes, but has now become a runaway menace.

GLORIOUS BLOSSOM – OR JUST A BLOOMING PEST? - (Photo by Steve Coe)

Throughout the Western Cape and particularly the South Peninsular the Port Jackson (PJ) is arguably the most successful and problematic of the plant invaders. This is mainly because of its fast rate of growth, a high reproductive rate and its ability to survive fires by coppicing. Indeed, fire is the main ally of this unwelcome plant invader. PJ’s seeds remain viable after a fire and the seedlings return at a shocking rate, even after the most horrific fires – establishing themselves at a furious rate, covering the entire burnt area, before the native flora has a chance to even get started.

PORT JACKSON SEEDLING – Acacia saligna (Photo by Steve Coe)

The Port Jackson does not have true leaves and what we are seeing in the photo above are actually leaf stems (Phyllodes). From August to October Port Jacksons comes into flower and are covered in masses of bright yellow, fluffy inflorescence, which are shortly followed by bean like seed pods. The seeds are spread by wind, flowing water and by the passage of vehicles and other human activity. Much of the invasion of new areas (and re-colonization after clearing) takes place along the verges of roads.

PORT JACKSON SHOWING INFLORESCENCE AND SEED PODS (Photo from Plant Invaders (1978) - Botanical Research Institute Handbook)

Port Jackson (PJ) does not produce true flowers, but instead displays masses of fluffy canary-yellow inflorescence, that will in time produce thousands upon thousands of virtually fire proof seeds. These start to develop in drooping seed pods, even before the inflorescence has run its full course. As we have said, these seeds are incredibly viable and are the secret of PJ’s incredible success as an invasive species.

BLAZING BLOSSOM TODAY – BLAZING WILDFIRE TOMORROW (Photo by Steve Coe)

As explained, the control of Port Jackson is not simple as the wretched plant coppices readily, after being cut down (or burnt), which results in an even greater proliferation of plant material. The plant and its roots must be removed entirely or an approved chemical herbicide must be painted onto the cut area. It has soft wood, not suited for firewood as it burns too fast. In a following article by Jeremy Croudace, the correct procedure for eradicating this pest is explained in more detail.

NODULES ON PORT JACKSON FROM PARASITIC WASP (Photo by Steve Coe)

Many Port Jackson shrubs, such as the young plant in the photo above, are characterized by the appearance of hanging brown nodules on their branches. These are the result of attack by an imported microscopic wasp. This wasp is a specific parasite of the Port Jackson and were released amongst these alien shrubs, a few years ago, as part of biological control programme, that has arguably shown some limited success.

NOTE : IT IS AN OFFENSE TO HAVE THIS PLANT ON YOUR PROPERTY – ERADICATE IT ON SIGHT.

Click on the specific plant below to see photo and description:

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• Hakea
• Australian Myrtle
• Manotoka
• Gum Tree
• Pampas Grass