Australian Weeds in Australia

1. Case Study - Southern Victoria

The following article was published in the September 1990 issue of the Newsletter of the Victorian Region of SGAP. It describes the efforts of a group of dedicated environmentalists in tackling a weed infestation problem along the south coast of Victoria. Mary White, referred to in the article, died in 1996 at the age of 85.

Melaleuca hypericifolia (and other weeds)

Judy Barker

From June 11 to 17 it was Weed Week for Angair (Anglesea and Airey's Inlet Society for the Protection of Flora and Fauna). During this strenuous week of fourteen sessions (morning and afternoon), volunteers remove "weeds" from the sensitive coastal and heathland environments. Mary White, president of Angair, not only supervises but takes vigorous part in this activity.

I went to four sessions and was surprised at how much was achieved as well as the extent and range of weeds present. At one session we removed Leptospermum laevigatum from a beautiful area of coastal heathland which was vibrant with the pinks of Epacris impressa, the yellow cones of Banksia marginata and the greenish-white propellers of Spyridium vexilliferum. At Point Roadknight we sawed off and removed the slender trunks of Melaleuca lanceolata that had been snapped off by vandals and left hanging. This is now a pretty, well mossed area with many small herbs returning since Mary and others have almost eradicated the Myrtle-leaf Milkwort (Polygala myrtifolia) that threatened to dominate this part of the coastal strip.

Another session was devoted to the removal of garden weeds, such as gazanias and succulents, which had just been dumped in the nature reserve instead of taken to the tip. We also pulled out seedlings of Coprosma repens, ltalian buckthorn (Rhamnus alaternus), and Senecio elegans from behind the dunes.


"Insidious Beast"

Around the camping ground at Anglesea we had an energetic go at boneseed, coprosma and scattered plants of smilax asparagus (Myrsiphyllum asparagoides) until we were overcome by expanses of this last insidious beast just scrambling over everything. Mary surveyed it grimly and said 'We'll leave that to the authorities'.

   Melaleuca hypericifolia
  

Melaleuca hypericifolia is a good example of how even an apparently benign plant can become a pest under suitable conditions. The species is widely cultivated in many areas without problems. Photo: Brian Walters

One session made an indelible impression on me. Five of us tackled an area within the grounds of the Scout Camp which had been planted with ornamental Australian natives some time before the Ash Wednesday (1983) bushfires. We set to work to remove seedlings 30 to 60cm high of Melaleuca hypericifolia and M.armillaris. We kept our heads down because if we looked up the hopelessness and immensity of the task almost overcame us. Fortunately, the preliminary attack was merely a lesson. Mary soon took us to the margin of this area, to a part where we could make some obvious improvement.

This is one of my favourite habitats - heath-woodland, where sweet little plants like hibbertias, heaths, leucopogons, goodenias and dillwynias carpet grey, sandy soil under stringybarks. It is open, generous, friendly bush.

After the fires, the area around the planted shrubs had been taken over by millions of their seedlings. Now there was an area larger than a suburban block entirely covered by the stout stems of Hakea laurina, H.drupacea (syn. H.suaveolens), Melaleuca armillaris and M.hypericifolia, ranging in height from 0.3m to 3m and quite impenetrable. Apparently this will be tackled by machinery at some future time.


Home groan...

Next day my husband and I spent an unscheduled session on our own block where I had been ill-advised enough to place two innocent plants of M.hypericifolia before the fires. It took us three hours to root out the two huge originals and the seedlings from our block and the block next door. And a large M.armillaris seedling -- I had not planted that! Next time we go to our property we have an even longer job ahead of us: the removal of Kunzea ambigua. The horde of little (and big) kunzeas resulted from only two original plants.

In such sensitive environments it is a pity that the general public is not warned of the problem by local nurseries.

Thirty-four volunteers took part in Weed Week and logged one hundred and fifty-six hours. They have done a most valuable job.




2. Case Study - Southern Victoria

The following article was published in the March 1989 issue of the Newsletter of the Victorian Region of SGAP.

Jumping the Fence - Two Garden Escapees

Kathie Strickland

   Billardiera heterophylla
  

The Western Australian bluebell, Billardiera heterophylla, is a popular light climber but has proven to be weedy in certain areas, particularly southern Victoria. White and pink forms are also in cultivation. Photo: Brian Walters

Weeds are opportunist species which can take advantage of open ground and colonise areas rapidly. They can achieve this by efficient survival techniques such as:

  • Production of numerous seeds
  • Rapid growth
  • Ability to withstand extreme conditions such as lack of shelter from wind and/or sun.

Many of our prized garden specimens can become weeds once established amongst native bush species. Even native species can become weeds when growing in a different habitat. Any change to the environment can alter a plant's habits. One example of this is the proliferation of "Sweet Pittosporum", Pittosporum undulatum, following the introduction of the European blackbird. This bird eats the Pittosporum fruits and distributes the seeds over a wide area.

Another pest is the Western Australian bluebell Billardiera heterophylla (formerly Sollya heterophylla). This species also produces copious seeds which are thought to be eaten by the blackbird and the Indian Myna, and again distributed far and wide. A result of this, to give one example, is the proliferation of the species,at "Seawinds" on the Mornington Peninsula, southern Victoria. This climber grows rapidly in the native vegetation, entwining through other species present. It could possibly pose as great as a threat as Boneseed, Chrysanthemoides monilifera, a problem with which many people may be more familiar (see "Exotic Weeds in Australia").

The WA bluebell is a favourite of many gardeners, with its dainty blue flowers and it is often sold in nurseries. It is a popular garden plant, often grown in total ignorance of its ability to colonise native vegetation to the detriment of the local bush.

Both of the native plants quoted here produce copious seeds which enable them to spread rapidly. Maybe we should become more aware of the characteristics of weeds and become more wary of planting such species in areas which are close to native bush.

Note: In South Australia, Billardiera heterophylla is now a declared weed species that must be controlled - it is banned from sale in that State (for further information see this Declared Plant Policy).




3. Case Study - Western Australia

The following list was compiled by Greg Keighery for his "Annotated list of the naturalised vascular plants of Western Australia" (see Further Information) and was contributed by Rod Randall of the Weed Science Group, Agriculture Western Australia.

Extending their Boundaries

Western Australian plants causing problems in.........Western Australia

The following are all Western Australian native plants which have become weedy somewhere in Western Australia. Many are popular in cultivation and this reinforces the need for care in plant selection.

  • Acacia blakelyi
  • Acacia lasiocalyx
  • Acacia microbotrya
  • Agonis flexuosa
  • Calothamnus validus
  • Ceratopteris thalictroides
  • Chamelaucium uncinatum
  • Calothamnus quadrifidus
  • Eucalyptus conferruminata
  • Hakea costata
  • Hakea francisiana
  • Hakea pycnoneura
  • Melaleuca lanceolata
  • Melaleuca pentagona
  • Nymphaea gigantea
  • Ottelia ovalifolia var. chysopetala
  • Solanum hoplopetalum
  • Solanum hystrix
  • Vallisneria gigantea
  • Verticordia monodelpha
Hakea francisiana    Chamelaucium uncinatum
Left - Hakea francisiana. Right - Chamelaucium uncinatum Photos: Brian Walters


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