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'Native' weeds of Halls Gap

Halls Gap Landcare has completed a review of weeds that are posing risks to the unique biodiversity of the Gariwerd/Grampians Ranges. You might be surprised to learn that four of their top 10 species are native to Australia!

They are each Australian plants, though not locally native to the Gariwerd/Grampians region. So why do we still consider these plants exotic weeds, just as problematic as European species like blackberry? Plants have evolved many ways to move long distances naturally, via the wind or on animals. Species ranges aren't static and can shift, so who's to say these species couldn't make it to our region naturally? While this is not out of the question, it comes down to the speed that plants can now travel and establish, thanks to the activities of humans. Without assistance from humans, 'pioneer' individuals that end up far outside their range through wind or animal movements tend to have a hard time getting a foothold in, particularly if there are not many open unclaimed gaps in the habitat for them to take advantage of.

When we think of exotic weeds, we tend to think of species from overseas, like this blackberry, rather than Australian species.
When we think of exotic weeds, we tend to think of species from overseas, like this blackberry, rather than Australian species.

But when we get humans involved, natural movement of species gets 'super charged.' They can cross greater distances than ever before, hitchhiking on our clothing, or vehicles. Once they arrive at their new destination, humans once again make it easier to establish, as our activities tend to create disturbed sites, free of competitors, that are perfect for them to colonise. Then if it turns out these locally exotic plants have some competitive advantage over the locally native plants, they can emerge as destructive weeds.

Some plants have it even easier - they don't even need to hitchhike. They just need to be pretty enough that we drive them across the country and lovingly plant them in our gardens! This is true of these four species - each is a lovely beautiful Aussie plant that got its start in the Gariwerd/Grampians region as garden ornamentals. And then each has been able to capitalise on some advantage it holds over the local native species, to start replacing the diverse native communities with dense patches of this single exotic species.

Some weeds are really quite pretty, like the Cootamundra wattle with its intense yellow blooms, which has certainly contributed to their spread as ornamental garden plants. But the problem is they don't just stay in your garden! Image credit: Graeme Lunt (CC-BY) via iNaturalist.
Some weeds are really quite pretty, like the Cootamundra wattle with its intense yellow blooms, which has certainly contributed to their spread as ornamental garden plants. But the problem is they don't just stay in your garden! Image credit: Graeme Lunt (CC-BY) via iNaturalist.

For example, research has shown that Bluebell creeper, native to Western Australia and ornamentally introduced in eastern Australia, experiences lower grazing pressure than our locally native Billardia species, giving the exotic a competitive edge. (Taylor, D.B.J. 1997. Ecology of the environmental weed Sollya heterophylla Lindl. in south eastern Australia. B.Sc. (Hons) thesis, La Trobe University).

Sallow wattle is another Australian species that has become a major problem here, as it absolutely thrives in our sandy soils, creating dense thickets that outcompete all else.

Dense thickets of sallow wattle have spread along creek lines in Rose's Gap, Gariwerd/Grampians Ranges. Image credit: Reiner Richter (CC-BY-NC-SA) via iNaturalist.
Dense thickets of sallow wattle have spread along creek lines in Rose's Gap, Gariwerd/Grampians Ranges. Image credit: Reiner Richter (CC-BY-NC-SA) via iNaturalist.

There's another reason we are being particularly protective of Gariwerd/Grampians - the ranges are one of Australia's biodiversity hotspots. In fact, 1/3 of all of Victoria's plant species are found here! And many of these species are 'endemic', meaning they are found no where else. So if we don't protect their homes here, we could loose those species entirely. That is why Halls Gap Landcare is encouraging locals to choose locally native plants for their gardens. While these Aussie ornamentals are beautiful, we have plenty of beautiful plants that are locally native to Gariwerd that we could adorn our gardens with instead!

The Gariwerd/Grampians ranges is unmatched for plant biodiversity in Victoria.
The Gariwerd/Grampians ranges is unmatched for plant biodiversity in Victoria.

Halls Gap Landcare has created a handy brochure that provides info on each of the priority weeds they identified, including these four Australian species. You can get a copy from the group in the new year. In the meantime, here is some further information on each of the four Australian species that are considered exotic and damaging weeds to Gariwerd/Grampians:

Sallow Wattle

Acacia longifolia

An Australian species but does not belong in this area. Invades woodlands and will take over large areas if not controlled. Flowers in August and September and produces large numbers of seeds spread by ants and birds. Cut off at ground level below the lowest node or cut and paint. Treat before seed. Hand pull small seedlings.

Alternatives: Acacia retinodes is locally native and grows to a similar height.

Sallow Wattle, a priority weed identified by the Halls Gap Landcare. It is native to Australia, but not to the Gariwerd/Grampians region, and was introduced here as a garden ornamental. It has been creating dense thickets along creek lines, crowding out other native species. Image credit: Nick Fitzgerald (CC BY NC) via iNaturalist.
Sallow Wattle, a priority weed identified by the Halls Gap Landcare. It is native to Australia, but not to the Gariwerd/Grampians region, and was introduced here as a garden ornamental. It has been creating dense thickets along creek lines, crowding out other native species. Image credit: Nick Fitzgerald (CC BY NC) via iNaturalist.

Yarra Burgan

Kunzea leptospermoides

Medium sized shrub, soft to touch, with aromatic dark green foliage and small white flowers with a burgundy centre, seen in December. An Austalian species, similar in appearance to other tea trees, but does not belong in this area. Spreads easily, outcompetes other local native plants and presents a high fire risk. Cut and paint, hand pull.

Alternative: Grampians Prickly Tea Tree, Leptospermum continentale

Kunzea, a priority weed identified by the Halls Gap Landcare. It is native to Australia, but not to the Gariwerd/Grampians region, and was introduced here as a garden ornamental. Image credit: Carol Page (CC BY NC) via iNaturalist.
Kunzea, a priority weed identified by the Halls Gap Landcare. It is native to Australia, but not to the Gariwerd/Grampians region, and was introduced here as a garden ornamental. Image credit: Carol Page (CC BY NC) via iNaturalist.

Bluebell Creeper

Billardiera fusiformis

An Australian species but does not belong in this area. A fast-growing scrambling climber with berries readily eaten by birds and mammals it spreads rapidly and smothers other local native plants. Cut and scrape or paint, or hand pull.

Alternatives: Common Appleberry, B. mutabilis and Running postman, Kennedia Prostrata

Bluebell creeper, a priority weed identified by the Halls Gap Landcare. It is native to Australia, but not to the Gariwerd/Grampians region, and was introduced here as a garden ornamental. Image credit: @ethmostigmus (CC BY NC) via iNaturalist.
Bluebell creeper, a priority weed identified by the Halls Gap Landcare. It is native to Australia, but not to the Gariwerd/Grampians region, and was introduced here as a garden ornamental. Image credit: @ethmostigmus (CC BY NC) via iNaturalist.

Cootamundra Wattle

Acacia baileyana

An Australian species but does not belong in this area. Spreads from seed drop and by birds. Grey-green foliage and clusters of bright yellow flowers in late Winter and Spring makes them tempting to plant, but spreads rapidly into local native forests. Requires cutting at ground level below lowest node to prevent resprouting.

Alternatives: Acacia retinodes is locally native and similar in size.

Cootamundra wattle, a priority weed identified by the Halls Gap Landcare. It is native to Australia, but not to the Gariwerd/Grampians region, and was introduced here as a garden ornamental. Image credit: @meygels (CC BY NC) via iNaturalist.
Cootamundra wattle, a priority weed identified by the Halls Gap Landcare. It is native to Australia, but not to the Gariwerd/Grampians region, and was introduced here as a garden ornamental. Image credit: @meygels (CC BY NC) via iNaturalist.
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Elia Pirtle

Landcare Facilitator and Communications Officer