Check what can stay and what must go before you pull up plants
An international weed, water hyacinth infests aquatic systems on every continent
One of the least favourite but essential chores that must be performed regularly in the garden would have to be weeding.
Because they are often attractive, easy-to-grow plants that thrive, weeds can quickly become invasive and destroy other less rigorous plants if they are left unchecked.
The Australian government has produced a national watchlist of plants that should be avoided in your garden at all costs.
If allowed to take root and spread, they quickly turn the backyard into an unkempt mess.
Manager of the government’s National Weeds Strategy Project John Thorp, says, ‘Weeds are any plants growing out of place, such as on paths, in lawns or in a home garden, that a person wishes to control.’
State of origin
Location is key in weed warfare, as species that are classified as a dangerous weed in a particular state or territory may be seen as a welcome garden plant in another.
‘Australia is affected in most places by weeds, but they change because we go from the tropics to temperate climates,’ says John.
‘What may be an indoor plant in Tasmania could easily be considered a weed in the tropics.
‘You also get subtropical vines which scramble over canopies.
‘They’re a problem, especially in the Macleay River area in New South Wales where they really damage the bushland,’ says John.
There are 32 weeds listed by the federal government as having national significance. Many, including the most common one, lantana, are referred to as garden escapes.
‘That is, they’ve literally escaped from the garden,’ explains John.
‘Birds typically spread the plants by picking up the seeds and flying over the neighbour’s place, dropping a few along the way and eventually heading into bushland.
‘The culprits include a range of black birds like the currawongs, which are frugivores.’
Some of the most common backyard plants that turn into weeds this way include the fast-growing asparagus weed, which the birds prey on for their berries.
Other widespread garden weeds are brooms, which come in different coloured varieties but are most common with yellow flowers. All types of broom, regardless of colour, are prolific seed producers.
Cat’s claw creeper, Madeira vine and cacti are also garden weeds.
‘Cacti are a major problem if you are in a dry place,’ says John.
‘Australia was overrun at one time with a type of cactus, the prickly pear. The opuntioid cacti are a whole group of plants that could easily invade entire dry parts of Australia.’
To ensure the plants that are stocked are not dangerous to the environment, every Bunnings store has a Greenlife Buyer.
National Greenlife Buyer David Hardie says, ‘One of the key selection criteria is suitability for local climate and conditions.
‘Our team also works closely with regulators to ensure we are always stocking the right plants.
‘Bunnings is committed to not selling environmental weeds that may have a negative impact on the natural environment.’
David adds there are now more non- or less-invasive plant cultivars than in the past and recommends the state and territory plant guide at, Grow Me Instead.
To control weeds, there is a wide range of herbicides and weedmats available instore. Mulching is a good way to prevent them occurring in the first place, as is cutting spent flowerheads from plants.
Cat's Claw Creeper is a garden weed. Image: Alamy
Once a plant becomes a concern, it needs to be eradicated completely by preventing seeding and reproduction.
‘But the real problem with weeds spreading and propagating isn’t the birds, it is humans incorrectly disposing of garden waste,’ says John.
‘Many people dump waste in the bush or recycle clippings as mulch thinking they’re being green, but it’s really just spreading weeds further.
‘The correct disposal method for a large amount of material is using an enclosed system like a skip bin, or taking the waste to the tip, making sure that it is tied down securely in a trailer.
‘Otherwise, use the green bin and dispose of clippings, weeds and other waste material through your normal rubbish removal service.’
John also gives the big thumbs down to the backyard burn-off.
‘It is illegal in many parts of Australia, especially in summer, and the heat from a burn-off opens seeds so they can germinate. Weed residue can also be carried in the smoke.’
Weeds are also a major problem in waterways, as they damage and pollute delicate aqua ecosystems.
‘Athel pine is a shade tree which people use in arid lands,’ says John.
‘It becomes weedy and, like the water hyacinth, which was once an attractive pond plant with its blue flowers, it invades major watercourses.
‘They are presently trying to control 600km of it in the Finke River, which is the largest dry river in the world, running from above Alice Springs to below the South Australian border.
‘These trees are often found in recreation areas, caravan parks and the banks of rivers,’ says John.
Many of the 100 willow tree varieties pose a double threat as they grow on both land and water.
‘Willows have a very short seed life, from two to six weeks, and this very brief propagation period means they can cross-pollinate and produce seed rapidly, so they’re now threatening our waterways.’
The vigour of a weed’s growth depends on which time of year the rainfall occurs. For most of southern Australia, this would be in spring and for the tropical north in summer.
Regardless of location, rainfall and season, once any type of weed takes hold, it’s hard work getting rid of it.
‘If you are going to successfully keep weeds down, you can never take the pressure off, as it requires dedicated persistence to keep them under control,’ says John.
The Sydney Weeds Committee offers advice on how to weed manually.
Always wear gloves and use a hand trowel to remove the entire root so the plant can’t resprout from any remaining root system.
RAKE background mulch.
INSERT the trowel and carefully loosen the soil around the roots.
PULL the plant free, grasping it by the stems or the leaves while freeing the roots with the trowel.
REMOVE the plant and shake off the excess soil.
REPLACE the disturbed soil and any ground mulch.
Place the entire plant or any part capable of reproducing, such as tubers, rhizomes, berries, seeds or other propagules in a bag and remove from the site. Other debris material can be mulched on site.
Dandelion weeds. Image: Thinkstock
Nine national weeds
Asparagus weed. Image: Alamy
Blackberry. Image: Thinkstock
Broom. Image: Thinkstock
Lantana. Image: Thinkstock
Mimosa. Image: Thinkstock
Parthenium. Image: Thinkstock
Salvinia. Image: Thinkstock
Water Hyacinth. Image: Thinkstock
Willow. Image: Thinkstock