Australia’s diverse climate is home to countless beautiful plant species, but it also hosts a range of dangerous and invasive plants. These plants can threaten native ecosystems, harm livestock, and even pose serious health risks to humans. At PlantArk, we believe in celebrating all kinds of flora while staying informed about potential hazards. Below, we’ll explore ten problematic species, how to identify them, and tips on controlling or disposing of them safely.
1. Black Nightshade (Solanum nigrum)
Description:
- A branching herb that can grow up to 75 cm tall. It has oval leaves with wavy edges and small, white or pale violet star-shaped flowers.
- The berries start green and turn black when ripe.
Where It Grows:
- Commonly found in disturbed soils, gardens, and crop fields throughout most of Australia.
Why It’s Dangerous:
- Contains toxic alkaloids (especially in unripe berries and leaves).
- Poisonous to humans and livestock if ingested in large amounts, causing gastrointestinal and neurological issues.
How to Identify:
- Look for clusters of small, round berries that turn glossy black.
- White or light purple flowers with a yellow centre.
Control & Disposal:
- Pull up seedlings or shallow-rooted plants by hand (wear gloves).
- Dispose of plants in a sealed bag to prevent berry spread.
- For larger infestations, consult local weed management authorities for approved herbicides.
2. Lantana (Lantana camara)
Description:
- A woody, scrambling shrub with square-shaped stems and small, clustered flowers in vibrant shades of pink, yellow, orange, or red.
- Leaves have a strong, pungent smell when crushed.
Where It Grows:
- Prefers warm, moist conditions—commonly found in coastal and subcoastal regions, forest edges, and disturbed areas.
Why It’s Dangerous:
- Forms dense thickets that outcompete native plants.
- Toxic to livestock (especially cattle), causing liver damage and photosensitivity.
How to Identify:
- Look for the characteristic multi-coloured flower clusters and rough, serrated leaves.
Control & Disposal:
- Small plants can be hand-pulled (roots and all).
- Larger infestations may require targeted herbicide or mechanical removal.
- Ensure all cuttings are bagged to prevent re-rooting.
3. Parthenium Weed (Parthenium hysterophorus)
Description:
- An annual herb with small white flowers, growing up to 1.5 m tall.
- Leaves are pale green and deeply lobed, giving them a feathery appearance.
Where It Grows:
- Thrives in disturbed soils, roadsides, and paddocks, especially in Queensland and northern New South Wales.
Why It’s Dangerous:
- Highly invasive and fast-spreading.
- Can trigger severe allergic reactions (skin rashes, respiratory issues) in humans.
- Toxic to livestock, tainting milk and meat.
How to Identify:
- Look for white, daisy-like flower heads and greyish-green, lobed leaves.
Control & Disposal:
- Hand-pull young plants (wear protective clothing).
- Use herbicides recommended by local councils for larger outbreaks.
- Prevent seeding by removing flowering heads before they set seed.
4. Paterson’s Curse (Echium plantagineum)
Also Known As: Salvation Jane
Description:
- A rosette-forming annual with tall, upright stems covered in purple or bluish funnel-shaped flowers.
- Leaves are hairy and rough to the touch.
Where It Grows:
- Common in pastures and roadsides across southern and eastern Australia.
Why It’s Dangerous:
- Toxic to livestock, causing liver damage (especially in horses and pigs).
- Can cause allergic reactions in some people who handle it.
How to Identify:
- Vibrant purple-blue flowers in clusters on spike-like stems.
- Distinctive hairy leaves that form a low rosette before flowering.
Control & Disposal:
- Hand removal is easiest when the plant is young.
- Mowing can reduce seed production but won’t eradicate established plants.
- Consider approved herbicides for large-scale control.
5. Oleander (Nerium oleander)
Description:
- An ornamental evergreen shrub that can reach up to 4 m in height.
- Leaves are long, narrow, and leathery; flowers range from white to pink or red.
Where It Grows:
- Often planted in gardens and public spaces across warmer regions of Australia.
Why It’s Dangerous:
- All parts of the plant are extremely poisonous to humans and animals if ingested.
- Even smoke from burning oleander can be toxic.
How to Identify:
- Look for thick, glossy leaves and clusters of trumpet-shaped flowers.
Control & Disposal:
- Use gloves and protective clothing when pruning or removing.
- Bag all clippings—never burn them.
- Seek medical attention immediately if ingestion or severe contact occurs.
6. Castor Oil Plant (Ricinus communis)
