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There’s no doubt that native plants are the best options for your backyard and garden. They promote biodiversity, provide a home for wildlife, and, of course, look absolutely beautiful.
However, there have been some instances where native shrubs and trees have caused more havoc than expected, and reached a point in growth that is deemed as ‘invasive’. Although it seems completely counterintuitive, native plants can become weed-like, and spread to take over gardens and any other plants in their way.
So, how does this weird phenomenon occur, and what plants should you watch out for? Let’s find out together.
Can native plants become weeds?
Unfortunately, the answer is yes.
Although native plants are definitely the preferred choice for creating biodiverse gardens, when planted in the wrong environment, they can spread like nobody’s business.
Kathie Strickland from the Australian Native Plants Society report on Environmental Weeds in Australia describes their weed-like behaviour as the following:
“Weeds are opportunist species which can take advantage of open ground and colonise areas rapidly. They can achieve this by efficient survival techniques such as:
- Production of numerous seeds
- Rapid growth
- Ability to withstand extreme conditions such as lack of shelter from wind and/or sun.”
According to the Eurobodalla shire council, “Native plants behaving as weeds can be more dangerous to native vegetation than some exotic species, because they are already adapted to Australia’s soils, and reproducing after fire.”
Why native plants can be invasive
Native plants can become invasive when planted outside of their endemic region. While many native plants are grown “outside the part of the country in which they occur naturally,” there are some that tend to exhibit invasive behaviour due to their spreading and intense growth in non-endemic areas.
The CSIRO report for WWF explains that “In the 1970s, widespread planting of Australian native species in public and private gardens took place, often with little understanding of how native plants would perform in horticulture.”
Over time, native plants that were popular and planted in homes, council areas and public places en masse have become like weeds and spread to take over everything in their path.
Which Aussie natives should you avoid?
According to Phys.org, native invasive species can “crowd out other native endemic species, affect the local balance of insects and other animals, wreck soils and even increase fire risk.”
There are three native culprits that have been reported across Australia to be invasive and express extreme weed-like behaviour.
It is recommended to avoid planting these three plants in your garden:
Cootamundra wattle (Acacia baileyana)
Cootamundra wattle is a beautiful golden tree that can grow up to 10m high. With a large spreading crown and lots of ball-shaped yellow flowers, it has been extensively planted in gardens and farmland as shelter belts.
This wattle variety competes with other native plants, including shrubs, small trees and groundcovers, and is a serious threat to woodlands across Australia. According to Weeds Australia, “Beyond its native range, it invades woodlands and forests in drier areas where annual rainfall exceeds 400 mm (Muyt 2001).”
Cootamundra wattle is spread through human involvement, as it is still commonly sold in nurseries, garden centres and markets. After being planted, this wattle has hardy seeds that are easily spread by birds and ants, as well as through farm machinery.
Sweet pittosporum (Pittosporum undulatum)
Sweet pittosporum was a popular garden plant because of its lush appearance and sweet-smelling flowers. While its natural range spans across the east of Australia, its use in gardens has spread into western Victoria and South Australia.
The Eurobodalla shire council explains that “The negative impacts of pittosporum come from the fact that it casts a dense shade which suppresses all other growth underneath it. Dense infestations of pittosporum can therefore turn into a monoculture of this species, with emergent eucalypts.”
Because of it’s quick spreading nature, due to birds spreading its seed, this plant is now becoming much more common in forest areas as well as urban ones.
Bluebell creeper (Billardiera heterophylla)
The bluebell creeper is a problem hailing from Western Australia. After being planted extensively in the eastern states for it’s attractive blue flowers, it has spread to overtake sandy coastal areas around Melbourne, as well as along the south coast of NSW.
It tends to clamber over other shrubs, as explained by the Eurobodalla shire council, and smother them in the same way exotic vines grow. “Because the creeper has evolved in the poor soils of Australia, it is likely to invade a much wider range of habitats than the exotic vines, many of which are restricted to the better soils found along creek banks and in other moist sites.”
How to reduce spreading of invasive native plants
Invasive native plants are tricky to overcome. They’re built for the Australian environment and climate, so getting rid of a surplus of invasive natives can be extremely difficult. The Australian Native Plant Society has explained the National Trust is involved with working towards removing these problem plants and endures to regenerate the bush back to its original state.
In your personal bubble, the best thing that can be done is not planting any invasive native species, especially in areas where they are not naturally occurring. The Australian Native Plant Society has a great list of both native and exotic flora species that can be referred to when purchasing, planting and maintaining your own garden.
It’s also a great idea to contact your local council to see whether they have any information regarding native invasive species that are common in your area, and should be avoided.
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