Invasive weeds are a serious problem for gardeners, farmers, and conservationists alike. Managing and eliminating weeds can take a significant amount of time and effort, so it helps to know exactly what you're up against.
Correctly identifying weeds can help you decide on the best course of action for eliminating them, including which products to use. That's why we've put together this guide to identifying and managing common Australian weeds.
Get help with weed identification as well as all the products and advice you need from All Green Nursery & Garden.
What is a weed?
A weed is any plant which has a negative impact and requires human action to control it. The negative effects of weeds can be on the environment, economy, human health, or the amenity of our gardens and landscaping. Weeds can also be a native or introduced species; native plants are usually considered weeds when they move from their natural habitat to a new area and begin to take over.
Weed identification chart
Here is our list of some of the most common Australian weeds and what you can do about them. If you don't see your weeds here, check out the Australian government's weed identification tool.
Bindii
Botanical name: Tribulus Terrestris
Locations: Australia wide
Description: Bindiis are the bane of anyone who has walked barefoot across grass in summer. It grows flat along the ground with stems up to 1 metre long with compound leaves and bright yellow flowers. The big problem with bindii weed is that it drops spiky fruit which can be annoying and painful.
Management: Look for outbreaks and weed out plants as they emerge. The best way to control bindiis is to remove before plant produces flowers and seeds.Use a prickle roller or foam rubber to collect and dispose of mature fruits. Herbicides are most effective at the seedling stage.
Milk thistle
Botanical name: Sonchus oleraceus
Locations: Australia wide
Description: Milk thistle or sowthistle is a common weed which grows annually. It can grow up to 2 metres tall and has yellow flowers and green stems and leaves. Milk thistle can be easily identified because the stems will leak a milky white sap when broken, hence the name. Milk thistle can also be a major host plant for aphids, and removing them will reduce aphid populations.
Management: Individual plants can be removed by hand, but make sure you remove all roots to prevent new plants re-establishing before the seed heads are formed.Herbicides are also effective in controlling milk thistle.
African boxthorn
Botanical name: Lycium ferocissimum
Locations: South-eastern states
Description: African boxthorn is one of the worst weeds in Australia because of its invasiveness and impact on the environment and agriculture. It is a dense woody shrub with red or orange fruit, rigid branches, and long spines. The fruit of African boxthorn may be toxic to humans and its spines can inflict painful injuries.
Management: Its spines make the boxthorn difficult to weed out manually. Pruning or mechanical control can be effective, although regrowth is likely. Herbicides can be sprayed during the growing phase or directly applied to each cut stem immediately after pruning.
Asthma weed
Botanical name: Parietaria Judaica
Locations: New South Wales, Victoria, South Australia, Queensland and Western Australia
Description: Asthma weed is a many-branched herb which grows year-round up to 60 centimetres tall. Its stems are covered in dense, curled hairs, and leaves are green, glossy, and wedge-shaped. Contact with asthma weed can cause severe skin reactions, and its pollen causes asthma and hay fever. It also causes conjunctivitis and rhinitis.
Management: Take care! Wear long clothes, a dust mask or respirator mask, eye protection, and gloves when hand pulling this weed. Remove the entire root system to prevent regrowth. Herbicides are most effective when the plant is actively growing and before flowering.
Blue morning glory
Botanical name: Ipomoea indica
Locations: All mainland states except NT, mostly in coastal areas
Description: Blue morning glory was originally cultivated as a garden ornamental which has now escaped and can threaten native vegetation. It grows to form a dense ground cover or climbs high into canopies. It has large green leaves and vibrant blue flowers.
Management: The plant can be manually controlled by pulling up the roots and mulching heavily to discourage regrowth. Herbicides can be sprayed as a foliar where the plant forms a ground cover, or individual stems can be scraped and painted with herbicide.
Bridal creeper
Botanical name: Asparagus Asparagoides
Locations: Common across southwestern Western Australia and parts of Tasmania
Description: Bridal creeper is a significant and invasive weed which threatens native environments. It is a climbing herb which grows up to 3 metres high and can produce more than 1,000 berries per square metre. It forms a dense canopy which smothers native plants, and its roots form a dense mat which destroys other plants.
Management: Physical removal is labour intensive and often ineffective unless all rhizome roots are removed and destroyed. Herbicides can be more effective, but since bridal creeper often grows in areas with native plants, application must be done very carefully.
