Trees In The Wrong Place

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Wayward Willows

Our series on Trees in the Wrong Place wouldn’t be complete without visiting the Willow family (Salix spp.).

Originally from China, there are now 32 different species, subspecies and hybrids invading riverbanks and wetlands in temperate Australia.

Nearly all have become naturalised and are listed as Weeds of National Significance. A few species including Weeping Willow (S. babylonica) are not listed but are of great concern because they hybridise with other species flowering at the same time such as Pussy Willow (Salix cinerea) and Crack Willow (Salix fragilis var. fragilis). The resulting hybrids become very invasive and are practically impossible to identify.

Willows have had great economic and environmental impacts in south eastern Australia and millions of dollars are spent each year controlling infestations.

 

In the severe droughts of 1981, government departments actually planted willows to rehabilitate riparian zones on grazing properties where soil salination and erosion were an issue. Bundles of Crack Willow were simply poked in holes five metres apart along creek banks. Years later, the same teams were back removing the trees, which proved to be an almost impossible task.

Willows spread their roots into creek beds, slowing the flow of water and reducing aeration. They also form thickets which divert water outside the main channel causing erosion on vulnerable creek banks. In autumn, fallen leaves create a flush of organic matter further reducing water quality and available oxygen and directly threatening aquatic plants and animals. Gradually, native vegetation like River Red Gum disappears as do native animals depending on them for food and nesting hollows.

Planting Trees For The Future

With climate change effects and rising temperatures governments are under pressure to provide research for better landscape solutions to avoid mistakes of the past.

Victoria’s Royal Botanic Gardens has designed a world first Landscape Succession Plan to help people plant the right kind of trees in the right places to ensure the trees are long-lived. It uses modelling to make predictions on what the climate will be like in the next 20 years.

Director RBG Professor Tim Entwistle said the Gardens are not just about aesthetics, there is a strong focus on climate change, water sustainability and biosecurity. He said Botanic Gardens is responding and contributing by using its collections, doing research in the garden, and through education and learning.

There are two million visitors to the Melbourne Botanic Gardens each year including 35,000 school children.

“As a race, we may be able to bring down those levels and mitigate some of those impacts,” he said.

“We have 8,000 species and manage plant collections scientifically, understanding where they grow, the type of soil and so on. Our goal is to be able to transfer a landscape and collection and position to one that’s more resilient in accordance with climate predictions.

“People are shocked when they find out that Melbourne’s landscape will be similar to that of Dubbo by the year 2090. We can’t now plant for the climate that’s been here in the last few decades, we have to plan for what’s coming,” he said.

“Willows have had great economic and environmental impacts in south eastern Australia and millions of dollars are spent each year controlling infestations.”

“We can look at where a plant grows naturally and predict what will grow in the future. That’s what we are looking into at the moment to guide us in what to collect and this can be done across the world.

“We’ve always tried to grow plants outside their natural habitat. That’s what we do best in botanical gardens and we can use that knowledge to help others.”

Professor Entwistle said certain plants will have a weed potential with an increase in temperature but every new plant is run through a model.

Manager Horticulture at Cranbourne Gardens John Arnott said there are several Australian plants that have become weedy after being planted away from their endemic range.

“One of the most interesting would be Sweet Pittosporum undulatum – a native of Eastern Victoria with the common name of Native Daphne due to its exquisite perfume. “It was widely planted outside its natural range in the 1970’s and within a decade it had escaped from our gardens through birds dispersing the fleshy seeds. By 2000 our Native Daphne had become so widespread that very few areas in Victoria with rainfall above 650mm are devoid of this plant,” he said.

A study carried out at the Gardens in conjunction with economists at a local university analysed where and how carbon is stored in various trees. Different species were found to absorb different amounts of carbon; the fast growing eucalypts proved to be the quickest at carbon storing, and the older the tree the more storage. About half the carbon was stored underground in roots and in all kinds of bacteria and living organic matter.

December 3, 2019 / by / in ,
Goodbye African Tulip

Spathodea campanulata may be a treasured tree in its native homeland of Africa but, in Australia, it is a tree no longer welcome.

Once a popular ornamental tree, African Tulip was widely planted in yards and along footpaths for its shady rounded canopy and showy bright orange-red flowers.

Biosecurtiy Queensland deemed the African Tulip a serious environmental weed way back in 2003 due to its aggressive growth and ability to spread into natural areas.

Its long, horn-shaped seed capsules can hold up to 500 papery seeds with transparent wings. If this is not enough, the tree also has suckering abilities.

There were consultations with the Nursery & Garden Industry Australia (NGIA) and it was agreed the tree must not be given away, sold, or released into the environment without a permit. Nurseries or market traders in Queensland that sell African Tulips may have their stock seized and destroyed, and re-offenders fined.

The Biosecurity Act 2014 requires everyone to take all reasonable and practical steps to minimise the risks associated with invasive plants and animals under their control. Councils in Queensland also have an obligation to remove African Tulips from the landscape.

“The public has become more enlightened about the importance of taking care of our native bee populations, and that is providing motivation to remove weed trees such as the African Tulip.”

Many councils are replacing them with native species as part of staged work programs in natural areas, parks and streets, and property owners are encouraged to do the same voluntarily.

Recommended non-invasive native alternatives to the African Tulip ar Stenocarpus sinuatus (Wheel of Fire) and Brachychiton acerifolius (Illawarra Flame Tree).

However, drive around Brisbane and other subtropical towns in Queensland, and the chances are you will see this tree flowering brightly. Due to climate change, it is also now found growing further south.

A spokesperson from Biosecurity Queensland said State and Territory governments each have their own process for listing plants under their biosecurity or noxious weed laws. They are currently working with the Australian Government to harmonise biosecurity arrangements due to increasing public sensitivity to the impacts exotic plants have on the functioning of natural ecosystems.

Stingless Bees Under Threat

The African Tulip tree is of particular concern to beekeepers like Bob Luttrell, better known as Bob the Beeman, as it conceals a lethal threat to our stingless bees. Bob’s website provides useful material to those likely to come across stingless bees in their work of removing or working with trees, in the hope that in some way the information will help comprised colonies to survive.

Bob said stingless bees are very much attracted to the sprays of African Tulip flowers.

“Look closer and you will see the bees gathering pollen, and seemingly imbibing other plant secretions as well as nectar.

“Unfortunately, if you continue the examination into the flowers, you will find the result of that foraging for pollen and nectar – a collection of dead and dying stingless bees and other insects.”

He said studies in Brazil, where the tree is also a problem, found that the gathered pollen did not get back to the hives. So the attracted bees are killed before they can return.

“Unfortunately the mechanism of attraction is strong and the numbers of stingless bees can be quite large in areas where stingless bees are present,” Bob said.

“I know of no other tree that flowers for such a long period, many months through the winter period, and most of the year in the tropics. That alone sets it in a league of its own. It is an attractive food source for the bees, at a time when there is not a lot of choice. The bees that are killed are the most experienced foragers, the scout bees, that look for sources of food for the colony. Because they do not get back to the colony, no warning can be developed, so the loss of bees will continue.”

Bob said the public has become more enlightened about the importance of taking care of our native bee populations, and that is providing motivation to remove weed trees such as the African Tulip.

The Gold Coast City Council recently took the educational aspect one step further by assisting a community initiative to help Australia’s native bees. It has set aside $30,000 of funds from its ‘Our Natural City’ strategy to subsidise the purchase of native bee hives city-wide. Property owners on 1200 + square metres will be eligible for $250 to go towards their hive purchase. A typical bee hive only requires maintenance every 12-18 months and the Council also runs Stingless Bee Keeping workshops.

For more information see http:// www.goldcoast.qld.gov.au/gold-coast-biosecurity-management-plan-48963.html

Did you know?

Did you know that in its natural environment in Africa, Spathodea campanulata can survive between 50 to 150 years and has many uses: light brown wood is used for manufacture of paper, drums and carving; bark is used in treatment of rashes on the skin of newly born babies, as a laxative, and an antiseptic to prevent growth and development of microorganisms; open boat-shaped pods are used as children’s toys due to their floating ability; and the trees also provide shade in coffee plantations and also as live fences.

Reference:

“Insect Mortality in Spathodea campanulata” BEAUV. (BIGNONIACEAE) Flowers by Trigo. J. R. and Santos, W. F. dos Rev. Brasil. Biol., 60(3):537_538.

October 19, 2019 / by / in , ,
No Palm, No Harm

This is the call of wildlife carers along the east coast Australia who are regularly called out to rescue wildlife that has been injured or become entangled after feeding on Cocos Palms.

The Cocos or Queen Palm (Syagrus romanzoffiana) is native to Brazil in South America. Until the late 1990s this resilient, drought tolerant species was one of the most planted palms in Queensland and still features prominently in several historic (state heritage listed) sites including the City Botanic Gardens.

The Cocos Palm has become widely naturalised and can be found growing from Darwin to Hobart. This palm is now regarded as an environmental weed due to its ability to prolifically reproduce, creating thick carpets of seedlings that outcompete recruiting native species. It is commonly sited in urban bushland, riparian areas and dry eucalypt forests.

Like many Councils, Brisbane City Council has actively managed this palm’s weed potential by reducing the number of specimens on site to hold one representative collection only, and undertaking seed removal of these remaining trees.

While it is not a prohibited or restricted invasive plant under the Biosecurity Act 2014, it is a Class “R” under Council’s Brisbane Invasive Species Management Plan. This declaration encourages residents to actively reduce populations of this palm via complete removal.

One of the native animals most affected by the presence of Cocos Palms is the flying fox, often called fruit bat. Flying fox numbers have significantly decreased during the past 50 years; the Spectacled Flying Fox and the Grey-headed Flying Fox are now classified as ‘Vulnerable to Extinction’ on the Federal Government’s Threatened Species list.

Deadly Attraction

Ironically, by feeding on Cocos Palm fruit, flying fox populations are spreading the very seeds that are contributing to the mammal’s rapid decline. Flying foxes have the ability to cross-pollinate over great distances and carry fruit and seeds far away from parent trees. They can fly around 40 kilometres per hour and up to 50 kilometres each night.

Fruits occur in large clusters and consist of a hard nut surrounded with a thin layer of fibrous flesh that is orange and sticky when ripe. The fruit can be toxic for animals and the fibrous seeds can create gut obstruction or become wedged in the animal’s teeth, leading to a slow death by starvation.

Latest information shows that flying foxes are now suffering from the premature wearing of teeth due to availability of the hard seeds all year around.

Wildlife carers warn that the sound of noisy birds around a Cocos Palm could mean there is a flying fox trapped in the massive strappy fronds or it has its wing membranes damaged from the tough flower spikes.

Australia – lucky to have its flying pollinators

Australia is the only continent in which the dominant trees are pollinated largely by birds and mammals (some of which are highly mobile) as well as by insects. Australian plants invest very heavily in pollination compared with trees in Europe and North America, most of which are pollinated by wind.

Author Tim Low, talking about ‘Climate Change Myths’, points out that contrary to popular belief, many Australian plants won’t need to migrate in response to climate change. Fossil and genetic evidence suggests that eucalypts, banksias and many other woodland trees survive climate change in situ by producing genetically variable offspring, some of which prove well adapted to new climatic conditions.

This is made possible by very high investment in pollination, which sometimes occurs between different tree species, resulting in the rapid evolution of new eucalypts by hybridisation. Eucalypts hybridize on a scale unmatched by any other trees on earth.

“This palm is now regarded as an environmental weed due to its ability to prolifically reproduce, creating thick carpets of seedlings that outcompete recruiting native species.”

Flying Foxes:

  • Are very clean animals and constantly groom their fur and wing membrane.
  • Have a complex social system and spend their day in permanent tree-top communal camps.

Have more than 20 different calls for communication

  • Have old males guarding the boundaries of the camp keeping a look out for predators such as eagles and pythons.
  • Lyssavirus is not spread when flying foxes fly overhead or roost in trees; it can only be transmitted through deep tissue bites or scratches.

Gardening Australia television presenter Jerry Colby Williams says “our flying gardeners are a priceless environmental service that sustains our natural environment”. He urges gardeners to help save the species by getting rid of existing Cocos Palms or at least having the flowers cut off before they seed. “Any gardener who grows a Cocos Palm will be aware of how much seed they actually set – seed by the barrow load – and that’s the problem. They germinate wherever they fall.

“If you’re thinking of growing a feather palm, try growing a Bangalow, Foxtail or Norfolk palm instead. That way gardeners rooted to the earth can look after the flying gardeners as well,” he advises.

Top a Cocos

In bushland settings, individual palms can be destroyed by cutting the crown off below the lowest frond; it is not necessary to treat the stump with herbicide as it will not reshoot. In gardens and urban areas it is more visually appealing to remove the palm at ground level instead of leaving a stump.

For more info on Flying Foxes contact Bat Conservation and Rescue QLD – bats.org. au or WIRES Australian. Wildlife Rescue Organisation – http://wires.org.au

References

Low, T 1917, The New Nature: Winners and Losers in Wild Australia, New edition, CSIRO Publishing, Collingwood. Wild About Australia 2018, accessed 1 April 2019, www.wildaboutaustralia.com

August 23, 2019 / by / in , ,
Camphors – The Silent Killers

Camphor Laurels – the silent killers of biodiversity.

It’s been nearly 200 years since the first Camphor Laurel (Cinnamomum camphora) was planted in Australia. Native to Asia, the tree was introduced in the early 1820s and first recorded at the Sydney Botanic Gardens.

When people noticed its rapid growth and attractive light green foliage, it quickly became a popular tree to plant for much needed shade. In 1872, the introduction of Arbor Day saw hundreds of thousands of Camphor laurels being planted in schools, church and courthouse grounds and in council parks and gardens. Many of these long-lived trees still line streets of cities and towns today, some being heritage listed. Little did we know that this evergreen beauty would become the most invasive weed species ever to reach Australian shores.

New visitors to the North Coast Region of NSW would be unaware that the picturesque sea of light green they see spreading along creek lines and over hillsides was once a darker shade. The ‘Big Scrub’ covered 75,000 hectares and was the largest subtropical lowland rainforest in eastern Australia until it was cleared for agriculture in the 1840s. The contraction of dairying and banana farming since the 1960s has resulted in large areas becoming infested with camphor laurel. This region includes one of Australia’s 15 biodiversity hotspots and is considered the most biodiverse area in the state. It supports the greatest number of plant and animal species of any area of NSW, and includes the greatest number of threatened species.

The Camphor laurel has divided communities for many years and there have been heated debates as to whether century old trees should stay or be removed.

Gold Coast botanist and consultant David Jinks, like many others, has strong views about Camphor laurels; his work brings him into contact with them almost on a daily basis. He said the need for shade isn’t so immediate that it should override the lethal threat Camphors are to local biodiversity.

“They are a beautiful tree. Where I lived in suburban Sydney, I spent much of my childhood climbing them and I have no doubt they had a very strong impression and positive influence on my long-term career in and love of all things plants.

“But I’m now very aware of their rapidly increasing threat to our rapidly decreasing local biodiversity. Of all the threatening weeds, they are enemy No.1 – by a long-shot. And they’ve yet to reach their epic peak.

“Camphor Laurels are in almost every local vegetation type from urban to wilderness hinterland. I’m currently working on an 85 hectare hinterland property of mostly good bush. We thought we’d have a hundred or so Camphors to deal with but, 18 months later, we’ve killed nearly 400 seeding trees plus taken out thousands of saplings and seedlings. Of the many weed species on site, the only one at every monitoring plot is Camphor Laurel. I’m sure this could be repeated on every similar adjoining property.”

“The need for shade isn’t so immediate that it should override the lethal threat Camphors are to local biodiversity.”

David said Camphor laurel is, without doubt, a slow-motion silent killer of local biodiversity that most people don’t get to see. This highly invasive tree has a tendency to form single species communities and exclude most other desirable native vegetation.

“The only way to reverse the spread of Camphor Laurel is to kill as many trees as possible, as soon as possible. To be completely effective there must be no more Camphor Laurel seed to spread. Put the effort instead into immediate control.

Kill the Camphor Laurel and replace it with a fast growing shade tree,” David said.

A passionate artist and tutor Matty George with his prized turtle chainsaw carving at Camp Creative, Bellingen, earlier this year. Organisers had to reassure some participants that the Camphor laurel timber being used didn’t come from the controversial Church Street tree that was recently chopped down in the main street. Teddy Reynolds shows off dad Paul’s work of art at the chainsaw carving workshop at Bellingen.

A spokesperson from the NSW Department of Primary Industry said Camphor laurel has never been a priority weed at the state level because it is well established in NSW and is very commonly used as an ornamental tree and council street tree. It is therefore not a prevention target.

Weeds are regulated by NSW local government and any efforts to reduce numbers would have to be done at a local or regional scale. Regional Weed Committees prepare and maintain a priority weed list, which includes state priorities; however, it is up to each Regional Weed Committee to determine what is a regional priority for control programs.

Federal Government Grant for project on deflowering Camphor laurels.

The introduction of the Biosecurity Act 2016, which specifically focuses on the shared liability relating to the containment and control of weeds, has been encouraging for weed committees.

A federally funded project commenced in July 2017 to undertake research to scope a handful of chemicals to de-flower or prevent fruit from developing on Camphor Laurel.

The Weed Society of New South Wales Inc. reported in its newsletter ‘A good weed’ there would be potential to use this technique, if successful, on other species.

How To Kill Camphor Laurel?

Contact your local Weed Advisory Service for correct chemical application before cutting a 20-30cm high strip into the outer bark and moist cambium layer to expose the heartwood (approximately 3-5cm deep) all of the way around the trunk. Return to check for suckers in 3-6 months.

Other uses of Camphor laurels Camphor laurel is being trialled as a potential fuel biomass in a north coast cogeneration project to produce electricity. Proposals are advanced to use woodchip for fuel to generate electricity at the Condong and Broadwater Sugar Mill cogeneration plants. This will involve the harvest of camphor laurel on a significant scale to supply this project.

Camphor laurel can be a valuable resource as a commercial timber and is used for a range of products and furniture and various items that can be turned on a lathe.

May 29, 2019 / by / in