By Ethan Benedicto
An invasive plant that produces thousands of seeds has been attacking Lysterfield Park, with native flora in the 1400-hectare nature pocket in danger.
The Friends of Lysterfield Park, a volunteer group that works to conserve the park’s integrity as well as Legalise Cannabis MP Rachel Payne stated that the plant species, known as boneseed, is inevitably consuming the park.
Payne initially initiated the conversation at a Legislative Council meeting on 17 October, where, speaking on behalf of a member of the Friends, said then that there are “already one million boneseed weed trees in Lysterfield Park”.
“Boneseed originates in Africa, another continent in the southern hemisphere so it performs well in Australia, it’s a weed of national significance and it is reducing the biodiversity value of our beautiful Lysterfield Park,” she said.
Boneseed, which gets its name from the bone-coloured seed when dry, is capable of producing 50,000 seeds per plant, and according to Weeds Australia, has the potential to significantly increase and become much more abundant in native undisturbed vegetation.
This weed shrub can grow up to two to three metres high, with woody branched stems and leaves that are 20 to 70 millimetres long and 10 to 35 millimetres wide.
The yellow flower heads are in groups of three to 12 and are individually up to 30 millimetres in diameter with each flower producing five to eight bright petals.
“The number of boneseed shrubs in the park is doubling every three years, I’ve raised the threat to the park in Parliament and I’ve asked Victoria’s Minister of Environment and Outdoor Recreation Reserve, Steve Dimopoulos if the government will fund a comprehensive control program as soon as possible,” Payne said.
“Lysterfield Park with its beautiful lake, picnic areas, and cycle and walking tracks is too precious to lose.”
Dimopoulos, in response to Payne, said that it was impossible to erase the shrub.
“I am advised that complete eradication of this species is not feasible due to the highly mobile seed bank which is spread by birds, native animals and pest animals,” he said.
According to the Department of Environment and Conservation NSW, through their Boneseed management manual published in 2006, the plant was first introduced to Australia around the mid-nineteenth century.
The first recorded gardens were in Sydney in 1852 and Melbourne in 1858, where it was speculated to have become naturalised with self-sustaining populations in 1910.
A restoration ecologist professor from Federation University, Singarayer Florentine, said that the nature of invasive species, such as boneseed, makes them “extremely difficult” to eradicate, and that a more effective approach is to “minimise the elevated population”.
“Once an area’s got it [invasive weeds], unfortunately, that’s it, you’ve got it [but] one of the things you can do is to minimise the spread.
“Given that I research and that I also work with community groups, one of the best ways to counter this is something called evidence-based management; what we need to do is take a step back and see how big the problem is.”
A subspecies, called bitou bush, arrived in 1908, where, alongside the boneseed, were planted extensively with the goal of stabilising coastal sand dunes and for erosion control from the mid-1940s to the 1960s.
With the same goal of soil erosion control, boneseed was introduced to the You Yangs, and the Australian Institute of Agricultural Science (AIAS) estimated that around 405 hectares had been colonised by the plant by 1976.
By 2000 it was listed at rank 6 by Weeds of National Significance as one of the 20 most significant weeds in Australia.
Florentine added that a multi-pronged approach would be the most effective, where, for instance, the physical removal of these weeds should be followed by a restoration program to prevent seed droppings and the conclusive spread of more boneseed.
“Subsequent monitoring management is very important because if you pull the plant during November or springtime, and you come back next spring, there will be another thousand plants there, I can guarantee that,” Florentine said.
“The way to go is continuous management but also increasing the competition by planting natives and reducing the light intensity in a way that these weed species will not be able to grow as well.”
Dimopoulos added that Parks Victoria currently delivers several weed management programs in Lysterfield Park with a focus on the protection of key biodiversity assets.
“Programs include the removals of boneseed and other noxious weed species,” Dimopoulos said.
“Management of weeds such as boneseed is labour intensive, requiring direct application of an approved herbicide or manual removal.
“Parks Victoria will continue to monitor areas of high conservation value within the park and treat priority areas.”
Tony Forster from the Friends said that the government has an unsystematic approach to the infestation and that an overarching blueprint was needed.
“The government has a plan for 5 per cent to 10 per cent of the park, the priority areas, but what is the plan for the remainder of the park?” Forster said.
“Ignoring 90 per cent of the park is not a long-term solution, the longer the government leaves the infestation, the more expensive the problem will become to control.”
In addition to the large number of seeds produced and the role of wildlife spreading said seeds, according to Parks and Wildlife Service Tasmania, boneseed remain viable in the soil for over 10 to 15 years, in turn allowing more time for germination which would occur after solid disturbances and fire.
Against native plants, their dense canopy formation gives them a strong advantage, coupled with the shallow root system that allows them to absorb moisture from even lighter rainfall before it reaches the deeper roots of native flora.
Florentine said that the scale of the issue plays a big role and that if, for example, 50,000 hectares have been infested, “pulling all the plants out is not going to work”.
“There should be a landscape scale level of management, that is an integrated approach and you need to think about the sensitive nature of the park, whether there are any threatened or endangered species there.
“Then you can say, okay, there are spots there with threatened orchid species or plant species, then you might want to be careful about hand pulling those to develop some form of fire control areas, where you can then invest a suitable time to burn that area,” he said.
Even then, while considering using fire as a controlling agent against boneseed, and if parties from the State Government to the CFA were to effectively mitigate the spread of boneseed, Florentine said that subsequent management after treatment is still key.
“Fire can visually give you a fantastic impression when you look at it, but after two days all the plants have grown back, and within a week or two, and with rainfall, there’ll be a lot more seedlings that will come,” he said.
With a specific method already in place by the State, Forster remains adamant that decisive action should be taken as soon as possible.
“If this is neglected for three years, it will cost twice as much to address, and control this noxious weed now, because it is eating our beautiful park,” he said.
“Spend the money, invest in nature – this park is loved in the southeast.”
