Causes of weed invasion

Our Blue Mountains townships and villages perch on the ridges above some of the most biologically diverse, fragile and beautiful natural vegetation in the world.

People have dramatically altered our natural environment, and all human activities carried out in our townships affect our downslope bushland, our World Heritage National Park, and our streams and rivers.

Urban runoff: off the garden, into the bush

Stormwater rushes off all our hard surfaces — roads, roofs, car parks, garages, factories and driveways — carrying with it the pollutants and detritus of everyday life. These include oils and chemicals, rubbish and organic litter, soil from cleared land, fertilisers, pesticides, herbicides, sewage from overflows, weed seeds and animal faeces.

This stormwater cocktail enters the bush, erodes watercourses, silts creeks, and changes the nutrient levels of the soil. Most native plants are adapted to low nutrient conditions. High nutrient levels may impede their growth or cause them to die. Moist, fertile soil favours the growth of weeds and invasive species that replace native plants.

Weeds in bush where runoff enters
Silt-laden stormwater carries weeds into the bush.

Bush invaders: out of the garden — into the bush

Many ornamental plants have escaped gardens to become bush invaders.

Weeds spread their seed by:

  • wind
  • water
  • birds, or other animals
  • machinery or soil
  • explosive release
  • a combination of all of the above

Weeds can also do a slow creep into the bush by growing vegetatively.

All of the weeds on this web site are aggressive competitors with our unique native plant species. Weeds destroy the habitat of our unique indigenous fauna.

Dumping: over the fence, into the bush

Cartoon of man dumping lawn waste over fence
‘Not in my back yard.’
(Cartoon by Norman Yeend)

Dumping of garden waste can introduce weeds into bushland through seeds, bulbs and corms or plant fragments in prunings, grass cuttings, leaf litter or soil. Weeds may quickly grow and invade the bush.

Dumping is illegal and incurs penalties.  Removing of dumped material costs every rate payer.

Dumping Garden Waste FactSheet

Disturbance of light levels and soil

Any kind of disturbance of the original soil conditions leads to weed invasion. Disturbance such as clearing, excavating, slashing, mowing or burning creates opportunities for weed invasion through increased light levels.

Weeds are often prolific along roadsides, bushland edges, watercourses and tracks. Foot, vehicle and animal traffic through the bush can cause erosion and compaction of soil, and may introduce weed seeds.

 What’s wrong with weeds?

Weeds blanketing bush
Weeds like Morning Glory dominate and replace native plants.

Weeds are plants free of their natural predators which thrive in disturbed bushland conditions.

They compete vigorously with native plant species and frequently dominate and replace them. Weeds degrade and destroy the habitat of native fauna. They restrict animal and human access to tracks, creeks and waterholes. They reduce local biodiversity and can permanently change ecosystems. Early detection and eradication of weed invasion is the most effective treatment.

We can help by…

Weeds of the Blue Mountains Bushland brochure
Ask Council’s Bushcare Section for this free booklet by calling 4780 5528, or just download the PDF.
  • learning to recognise weeds
  • understanding how and why weeds spread
  • removing bush-invading plants from our gardens
  • choosing only bush-friendly garden species
  • composting and mulching green waste
  • disposing of other waste responsibly
  • keeping our gardens within their boundaries
  • retaining water on our blocks
  • choosing to use phosphorous-free detergents
  • using only organic slow-release fertilisers
  • mulching to improve water absorption and retention
  • keeping garden waste out of the road gutters
  • picking up pet waste and disposing of it responsibly
  • always keeping to tracks
  • joining a local Bushcare group with the link below