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Thursday 22 October 2026
Weed Spotter Newsletter – issue 47
Welcome to the latest Weed Spotter newsletter.
In this issue, we learn about a new Mexican feather grass study, salvinia making a comeback, the Australasian weeds conference, upgraded online Weed Spotter training, a spooky trend in weed growth and a focus on hawkweeds.
We hope you enjoy reading this issue of the Weed Spotter newsletter.
Please email us if you have any feedback on this edition or suggestions for future articles.
Reminder to Weed Spotters
If you are moving to a new house or changing your employment, the contact details Agriculture Victoria has recorded for you, including postal address and email address, may need updating. Please email weed.spotters@agriculture.vic.gov.au to avoid missing the latest newsletter.
The 2027 State prohibited weed wall calendar will be sent to all Weed Spotters who have ‘opted in’ to receive it. If you would like to ‘opt in’ to receive a copy of the 2027 calendar in December, please email weed.spotters@agriculture.vic.gov.au.
New to the Weed Spotters network?
Weed Spotters assist the Victorian Government by looking out for and reporting State prohibited weeds, which either do not occur in Victoria, or are present in small numbers and can reasonably be expected to be eradicated. These are a group of high-risk invasive plants that are declared under the Victorian Invasive Plants Classifications under the Catchment and Land Protection Act 1994. Agriculture Victoria is responsible for the eradication of State prohibited weeds.
The Weed Spotters program is for those who work in an industry/are part of a group where they are likely to spend time in places where State prohibited weeds could be found.
Putting Mexican feather grass seeds to the test
Mexican feather grass or MFG (Nassella tenuissima) is a State prohibited weed here in Victoria, but it is also declared noxious in all states and territories of Australia. In NSW, MFG is listed as prohibited matter, so Agriculture Victoria and the NSW Department of Primary Industries and Regional Development (DPIRD) are combining our powers in search of MFG’s secrets. MFG has not been extensively studied, unlike its Nassella relatives, so the more we learn, the more we are able to target our efforts towards eradication.
DPIRD is undertaking a project that will investigate seed biology, including emergence and persistence, of MFG seed to better understand the species. Surprisingly, no such study has ever been conducted for MFG! To support the project, Agriculture Victoria is providing the project’s most valuable and difficult-to-source asset: the seeds. DPIRD is hoping to have at least 3,500 MFG seeds to undertake the project. The seed was sourced from Agriculture Victoria’s MFG plant collection, used for educational activities including Weed Spotter training, and from several recently detected infestations around Melbourne.
Pictured: A box of seed packaged up ready for the trip to NSW.
Pictured: One of the source plants for the project from a recently detected infestation.
The project is currently in the early stages, with some germination tests already being undertaken in NSW. A field burial study started in July this year. Seed packets were buried in a well-secured area in the field to determine seed persistence over time. The seed packets will be extracted periodically for viability testing over the next 4 years. DPIRD has also provided a PhD scholarship on MFG. A potential PhD student has been identified and will commence in the coming months to work on biology, herbicide control and spread modelling.
We are very interested in the results and feel privileged to be able to assist our NSW colleagues in their endeavours. We will continue to supply seed as we can, so keep your eyes peeled this Spring for MFG, you too might be able to contribute to this project!
Salvinia makes a comeback!
Salvinia is back. With no reports during 2025 or over the summer of 2026, it seemed unusually quiet on the salvinia front. Then March arrived and the reports started rolling in.
Between March and early August, Biosecurity Officers followed up 6 reports of suspected salvinia, 4 of which had salvinia plants present when visited. Tracing investigations were conducted, leading to a total of 7 confirmed salvinia infestations this year. Reports originated from Melbourne, Healesville, Mount Evelyn and Wangaratta.
This level of activity is unusual for the cooler months, as salvinia detections are more common during warmer periods. The resurgence has kept Biosecurity Officers busy, with a steady stream of investigations and follow-up activities to work towards eradication of this highly invasive aquatic species.
The most concerning detection involved a commercial aquarium in Melbourne's outer east where salvinia was offered for sale. The case came to Agriculture Victoria’s attention after Biosecurity Officers responded to a Facebook Marketplace advertisement. During traceback investigations to determine the source of the plants, Officers discovered that a customer of the aquarium had unknowingly received salvinia among shrimp purchased from the aquarium. More than 2,000 salvinia plants were subsequently removed from the aquarium business.
Pictured: Salvinia has recently been found for sale resulting in the discovery of seven new salvinia infestations in Victoria.
This detection highlights the importance of preventing contamination within the aquarium and aquatic plant industries. As the infested stock originated from a Queensland supplier, Victorian Biosecurity Officers worked closely with Queensland government biosecurity staff to ensure the supplier was aware of the risks posed by salvinia and their regulatory obligations.
While every effort is being made to prevent further incursions, it is difficult to know how many people may have unknowingly received contaminated stock. As a result, salvinia may be circulating more widely than usual.
There are many species of salvinia worldwide, and they are not easy to tell apart. Only Salvinia molesta is declared in Victoria, so Agriculture Victoria conducts DNA testing to confirm the identity of all salvinia specimens we find. To date, every sample tested has been confirmed as the declared species Salvinia molesta, reinforcing the message that if a plant looks like Salvinia molesta, it almost certainly is.
The recent increase in detections is a timely reminder for hobbyists, retailers and the wider community to remain vigilant. When purchasing aquatic plants, shrimp or other aquarium products, whether online or in-store, keep an eye out for salvinia, particularly as a contaminant hidden among other stock. A careful check today could help prevent the next infestation.
If you suspect you have received or seen salvinia, please contact Agriculture Victoria by calling the Customer Contact Centre on 136 186, emailing Weed Spotters at weed.spotters@agriculture.vic.gov.au or using the online form linked below.
Sharing Victorian expertise across the Tasman
High Risk Invasive Plants team members Bec Schwinghammer and Kaitlin Wright recently travelled to Christchurch, New Zealand, to attend the Australasian Weeds Conference, where they joined weed management practitioners and biosecurity professionals from across Australia and New Zealand.
Kaitlin delivered two presentations, Forty Years of Eradicating Water Hyacinth from Victoria and Innovative Disposal: Case Study of a 1-Hectare Water Hyacinth Infestation, highlighting Victoria’s long-standing commitment, innovation, and success in managing one of the world's most invasive aquatic weeds.
Bec presented Victorian Weed Spotters: Where Curiosity Meets Biosecurity, highlighting the achievements of Victoria's Weed Spotters program and sharing key insights gained over its 20-year history. Her presentation showcased the important role that community members play in the early detection and reporting of new and emerging weed threats, demonstrating how public participation contributes to Victoria’s biosecurity efforts.
The conference provided a valuable opportunity to connect with our 'weedy friends across the ditch', exchange knowledge and learn from shared experiences. Discussions focussed on species of mutual concern, including alligator weed and Lagarosiphon, as well as the challenges and opportunities in preventing their spread.
Pictured: Kaitlin Wright presenting on water hyacinth at the Australasian Weeds Conference.
Pictured: Bec Schwinghammer presenting on Weed Spotters at the Australasian Weeds Conference.
Perhaps the greatest takeaway was the chance to connect with like-minded people from across Australasia who share a passion for weed management and biosecurity. Bec and Kaitlin returned inspired by the conversations, collaborations and innovative work showcased at the conference, bringing back new ideas and valuable connections to support Victoria’s ongoing efforts to protect against current and future weed threats.
Discover the new and improved Weed Spotter online training
The online Weed Spotter training module has recently been refreshed! The training now features a new look and feel, with updated content, features and functionality. In addition, the 3D plant models developed by NSW DPIRD have been incorporated into the relevant species profiles, providing an enhanced learning experience. If you haven’t yet completed online Weed Spotter training, now is the perfect time to explore the new and improved module.
The online training mirrors face-to-face training and was developed using the same training materials and content. It includes photos and videos of State prohibited weeds to help Weed Spotters become more familiar with these species. The course also provides guidance on how to report State prohibited weeds and features interactive quizzes and exercises to reinforce learning and build identification skills.
The course takes approximately 1 hour to complete, although the time required may vary depending on how thoroughly you explore the supporting materials. You can pause the course at any time and return later without losing your place.
Pictured: The new and improved Weed Spotter online training.
All Weed Spotters who successfully complete the training receive a set of State prohibited weed identification cards. Previous participants have shared the following feedback:
- 'The Weed Spotter training was really useful and well set out, I enjoyed completing it.'
- 'I thought the online training was really good. It didn’t take too long to complete, and the content was meaningful and provided a good introduction to the main issues for Weed Spotters to be aware of.'
- 'Loved the course!'
- 'It was a pleasure and very enlightening.'
- 'Thank you for providing access to the Weed Spotter training – I thought the course was terrific. It was clear, informative, and easy to follow.'
- 'I look forward to spruiking the online training to our local volunteer groups, it is very well set up.'
To access the training, visit https://learning.agriculture.vic.gov.au/ and create an account by selecting 'Sign up'. When registered, be sure to select 'I am a Weed Spotter' from the 'Why are you here?' drop-down menu. Once your account has been created, you can enrol in the Weed Spotter training course.
To ensure your training is recorded as complete, make sure you progress through to the final screen of the course, which triggers the completion notification. Upon successful completion, you will receive a set of State prohibited weed identification cards in the post. Participants also have the option to download a certificate of completion at the end of the training.
HalloWEED: The spooooky season! How seasonal variation can trigger rare behaviours and appearances in State prohibited weeds
With Halloween around the corner, it's a good time to share some of the strange and spooky adaptations we saw over last summer in our State prohibited weed collection and in-field infestations.
Plants respond to their environment. They grow more vigorously under favourable conditions such as warm temperatures, adequate moisture and suitable nutrient levels. State prohibited weeds are particularly adept at responding to environmental changes and taking advantage of favourable seasonal conditions.
Glasshouse anomalies
Several firsts were recorded during the 2025-26 summer, including the first-ever flowering of a suspected spotted hawkweed (Hieracium maculatum - identification to be confirmed) specimen.
Spotted hawkweed is a rare species in Victoria, with a single known infestation, first detected in February 2020. Agriculture Victoria also maintains 1 live specimen in its glasshouse collection. The species takes its name from the distinctive dark blotches on its leaves.
While other hawkweed specimens regularly flower in the glasshouse during summer, the spotted hawkweed never did, until March 2026.
Its yellow flower heads closely resemble those of other hawkweeds species, but the event was exciting, nonetheless. The flowering enabled seeds to be collected and submitted to Royal Botanic Gardens which should allow us to confirm the identification of this mysterious species.
Pictured: The new water hyacinth specimens from the Anakie infestation flowering in the glasshouse.
Pictured: The spotted hawkweed plant flowering in the Agriculture Victoria glasshouse.
Another flowering first came among the water hyacinth (Eichhornia crassipes) specimens. The aquatic weed thrives in warm conditions and nutrient-rich water, yet despite vigorous flowering detected in infestations across the State, flowering has been difficult to achieve in glasshouse specimens. During the season, new specimens from the recently detected Anakie infestation were added to the collection. In March 2026, those plants flowered.
Although the pale purple flowers are attractive and have contributed to the species’ spread through ornamental plantings, they also produce thousands of long-lived seeds, making water hyacinth particularly difficult to control and eradicate. The flowering event provided Agriculture Victoria staff with a valuable opportunity to bag flowers and collect seed for germination trials.
Field anomalies
Returning to spotted hawkweed, readers may recall that Victoria’s only known infestation was detected and treated in the 2019-20 season. Following the initial treatment, no further plants had been detected by Agriculture Victoria staff.
Hawkweed seed is generally thought to remain viable for around 5 years. Consequently, sites are typically monitored for 5 years without detections before eradication can be declared. The 2025-26 season was therefore expected to be the final eradication assessment for this infestation.
To the surprise of the Agriculture Victoria staff conducting the assessment, new seedlings were discovered during the inspection. The most likely explanation is that some viable seed remained following the initial treatment and that the 2025-26 season provided ideal conditions for the species, both the glasshouse and in the field!
Pictured: The alligator weed plant found with distinctive wavy leaf margins.
Pictured: The distinctive spotted leaves of the spotted hawkweed.
The infestation has reverted to Active status and will require at least another 5 years of monitoring before eradication can be considered.
Another unusual observation involved alligator weed (Alternanthera philoxeroides), a highly adaptable species capable of thriving in both aquatic and terrestrial environments.
It also exhibits significant phenotypic plasticity, meaning its appearance and growth habits can vary considerably, depending on environmental conditions.
In aquatic environments, alligator weed often produces elongated, upright stems and leaves. In frequently mown terrestrial environments, however, it can form prostrate mats with shortened stems and smaller leaves. This variability can make accurate identification challenging.
Despite these differences, key identifying features remain consistent. Alligator weed has hollow stems, lance-shaped leaves in opposite pairs, and papery white flowers that occur on stalks.
Even with extensive experience recognising the species’ variability, Agriculture Victoria staff encountered something they had never seen before: alligator weed with distinctive wavy leaf margins. Fortunately, the inspecting officers recognised the species’ other key identification features and collected a specimen for further observation in the glasshouse. The cause of this unusual leaf form remains unknown, but it serves as another reminder that weeds can sometimes behave in unexpected ways when seasonal conditions align in just the right way.
State prohibited weed species profile – hawkweeds
The entire hawkweeds genus is declared as State prohibited weeds under the Catchment and Land Protection Act 1994.
Hawkweeds are native to the northern hemisphere and have been serious environmental weeds in New Zealand, the United States, Canada, Japan and Patagonia, particularly in high-altitude environments. They can thrive across a wide range of temperatures, elevations and growing conditions, including gravel or acidic soils, full sun, partial shade and areas subject to frost or snow.
Hawkweeds are especially successful in overgrazed pastures and alpine regions, where they outcompete native vegetation and alter natural ecosystems. They are allelopathic, meaning they excrete chemicals that inhibit the growth of surrounding plants, giving them a competitive advantage.
The largest infestations of hawkweeds are found in the Victorian Alps, where three species of hawkweed are present: king devil hawkweed, mouse-ear hawkweed, and orange hawkweed. These species have also been grown as ornamental garden plants.
Hawkweeds are small perennial herbs with distinctive yellow or orange, daisy-like flower heads. Their leaves form a basal rosette close to the ground and are covered in stiff, bristly hairs. The stems contain milky sap and are also covered in stiff, bristly hairs. Flowering occurs from spring to summer, with flower stalks ranging from 15 to 45 cm tall depending on the species. Flower heads are 15 to 30 mm in diameter and have characteristic square-ended petals.
Pictured: Hawkweeds leaves are covered in stiff hairs.
Pictured: Hawkweed flowers have characteristic square-ended petals.
The 3 species can be distinguished by their flowering habits. King devil hawkweed produces clusters of up to 25 yellow flower heads on red-tinged stalks. Mouse-ear hawkweed bears single yellow flower heads on individual stalks. Orange hawkweed produces clusters of 5 or more bright orange flower heads.
All 3 species spread by seed, above-ground runners (stolons) and root fragments.
These reproductive strategies enable hawkweeds to establish persistent infestations, form dense colonies and outcompete other vegetation in suitable habitats.
Under the Catchment and Land Protection Act 1994, it is an offence to buy, sell or display a State prohibited weed in Victoria. However, people who voluntarily report State prohibited weeds growing on their land are generally not subject to legal action by Agriculture Victoria. By preventing State prohibited weeds from establishing and spreading, Victorians can save millions of dollars in lost agricultural production and weed control costs.
The potential harmful impact of these species to the environment, economy, our social amenity and in some cases human health, can also be reduced.
If you think you may have seen a hawkweed plant, then please report it to Agriculture Victoria by emailing weed.spotters@agriculture.vic.gov.au, calling the Customer Contact Centre on 136 186 or completing the online reporting form. It is important to never remove any plants yourself – Agriculture Victoria will ensure all State prohibited weeds are removed and disposed of safely.
More information
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