Siam Weed

Siam weed (Chromolaena odorata) is known to be one of the most aggressive and damaging tropical weed species worldwide. It has a phenomenal growth rate and massive seed production allowing it to outcompete native vegetation, horticulture and pastures. The leaves are toxic to livestock and moderate levels of consumption have led to aborted calves and in some instances, death. Siam weed can cause skin complaints and can trigger asthma.

Siam weed was first detected in the Northern Territory in 2019 and the Weed Management Branch has been working with landholders affected by Siam weed since this time. This has been possible partly through federal funding the WMB received for two projects: (1) to research the best methods of control for Siam weed, completed in 2023, and (2) to assist landholders with on-ground control of Siam weed. Both projects will cease in June 2025.

A DRAFT 10 year Weed Management Plan Siam Weed 2025 – 2035 has been developed that sets out the legal requirements for managing Siam weed on land in the NT. 

• These requirements are additional to the general duties under the Weeds Management Act 2001 that apply to all declared weeds. 
• Once this weed management plan is in place, landholders will be responsible for meeting these legislative requirements.
• The WMB seeks feedback on this DRAFT plan. Comments can be provided by completing the survey below or by email: weedinfo@nt.gov.au
• All comments received will be de-identified and published along with the final Weed Management Plan Siam Weed 2025 – 2035, unless you choose for comments not to be included.

Comments can be made until 22 January 2025.