Lantana camara forms vast, impenetrable thickets. The
stems are prickly and difficult to walk through; the foliage is
toxic to cattle, horses and humans; and the thick, aggressive
stands smother native bushland and effectively prevent any
regeneration by native plants. It is known to be allelopathic,
which means that it produces chemicals specifically designed to
retard the growth of other plant species around it. Efforts are
being made to try to control lantana using biological control.
Bellyache bush (Jatropha gossypifolia), a plant predicted
to become just as problematic as lantana, is now spread throughout
Queensland, Northern Territory and Western Australia. It is
declared in the Northern Territory and infests around one-sixth of
that region, but some of the worst infestations are in the upper
reaches of the Burdekin and around Charters Towers in northern
Queensland. Bellyache bush forms dense thickets which exclude
native plants and wildlife and is quite toxic.
Mother of millions or Bryophyllum
Mother of millions
Another highly toxic and recently declared weed is mother of
millions or Bryophyllum spp. This is a very popular
ornamental plant as it takes no skill or watering to grow. Merely
pulling the plant out is not enough and a bare-rooted plant can
survive for months. If you burn it you would do well not to inhale
any of the fumes as this may cause poisoning.
Parthenium can cause dermatitis, hay fever and
asthma Photo: Greg Calvert
Parthenium (Parthenium hysterophorus) is a herb that can
grow to two metres tall with carrot-like leaves and white flowers.
Although it can smother fields and will grow just about anywhere,
it is specifically targeted by many weed control agencies not
because of its environmental problems, but because it causes severe
dermatitis, hay fever and asthma in many people.
Yellow oleander or Thevetia peruviana , has also escaped
from manicured gardens and gone bush. Although not present in large
numbers yet, it could be dangerous to firefighters if they were to
inhale fumes from this weed during grassfires. Breathing smoke,
eating any part of the plant or even stirring your tea with a twig
can result in severe poisoning.
Chinee apple woodland with large pocket of
prickly acacia, south of Home Hill, Queensland Photo: Greg
Also known as chonky apple, Indian jujube or by its scientific
name Zizyphus mauritiana, this thorny tree comes from Africa
and southern Asia where it is a popular ornamental tree. They are
fast growing, fire and chain-saw resistant, form pure mono-cultured
stands and can reproduce rapidly. A single tree can produce
8–10,000 seeds a year. These seeds can be spread by floods,
cattle or by wildlife such as agile wallabies. Chinee apple is a
Class 2 declared weed in Queensland, which means landowners must
take reasonable steps to keep land free of the weed. This can be an
extremely expensive process but it is a job which many people are
now starting to confront in the north-east Queensland area.