Chilean Needle Grass mono-culture in the reserve east of Rivett Street, Hackett (2024).
Chilean Needle Grass (CNG), Nassella neesiana is a Weed of National Significance, a declared pest plant and environmental weed with a risk rating “very high” in the ACT and NSW. It occurs in the grassy ecosystems where it out-competes indigenous species and can transform grassy woodlands into Chilean Needle Grass woodlands.
It is regarded as one of the worst weeds in Australia because of its invasiveness, potential of spread, and economic and environmental impact. It is closely related to another Weed of National Significance, Serrated Tussock, Nassella trichotoma.
On Mt Majura and Mt Ainslie, CNG occurs mainly in areas with deep soil and a relative high availability of moisture such as at the lower slopes with endangered grassy woodlands particularly around nature reserve entry points, along tracks and behind backyards.
Deep Mulching – FoMM’s trial to help manage Chilean Needle Grass (CNG)
Majura Mountain Scouts spread mulch on top of dead CNG which FoMM volunteers sprayed with herbicide (26.11.2024).
Depending on available moisture, Chilean Needle Grass can produce 20,000 seeds per square meter and seeds can persist in the soil seed-bank for many years. An unusual feature of CNG is that in addition to the normal flower seeds, it produces hidden seeds which are formed in the nodes and bases of the flowering stems. These “sneaky” stem seeds are self-fertilised and enable the plants to reproduce despite slashing, grazing or fire.
CNG seedlings have a high survival rate and can produce flowers in the first season; the adult plants are long-lived and very hardy.
A large infestation of CNG spread around the Hackett water tank, along the drainage line and the back of Rivett Street residential properties.
The dispersal of CNG is assisted by regular slashing including during peak seeding time in summer to reduce fire fuel, and by local residents who spread grass clippings in the reserve (see for instance here and here).
In early 2022, volunteers of Friends of Mt Majura (FoMM) began a trial to control of CNG along the southern side of the drainage line, combining herbicide application with physical removal, mulching, and the planting and direct seeding of native grass and other groundlayer species.
The initially treated small patch of CNG with tussocks growing from direct seeded native grasses was encouraging (25.05.2025) …
The first results of the treatment of the initially small patch encouraged FoMM to scale up the trial to include the northern side of the drainage line, which by then had large patches of thickly growing CNG.
… and Friends of Mt Majura sprayed a larger patch with thickly growing mono-culture of Chilean Needle Grass with herbicide (25.05.2025), …
The approach involves the initial treatment of densely growing CNG infestations with herbicide (Glyphosate) to kill the adult plants, followed with placing a deep layer of wood chips on top of the dead plants.
The idea of placing mulch is to suppress the germination of CNG seeds stored in a massive soil seed-bank, thus reducing the new growth of CNG seedlings.
Over time, when the mulch decomposes, FoMM plans to direct seed local grasses such as Redleg Grass (Bothirochloa macra), Speargrasses (Austrostipa sp.), Wallaby grasses (Rytidosperma sp.), and Weeping Grass (Microleana stipoides) to provide a competitive ground cover.
… cut the long dead leaves (20.07.2025), …
For further information on FoMM’s CNG trial along the Hackett drainage line, visit the following Canberra Nature Map sightings with descriptions of some of the management actions volunteers carry out:
https://canberra.naturemapr.org/sightings/4623677
https://canberra.naturemapr.org/sightings/4668383
For further information on CNG including its dispersal and management, visit the Weeds Australia website at https://weeds.org.au/profiles/chilean-needle-grass/.
Please contact convenor@majura.org for inquiries.
Waltraud Pix
22 July 2025
Photographs by me, dates in brackets.
… and topped the treated and cut Chilean Needle Grass with a layer of wood chips (foreground); there are still many dead uncovered Chilean Needle Grass tussocks visible in the back (20.07.2025).
The July working crew gathers around a well earned delicious cake baked by Margy who is seen cutting the cake.
