Fireweed

• Annual or short-lived perennial herb.
• Plant varies greatly in size and shape depending on conditions.
• In dry harsh conditions, may be less than 20cm tall with narrow leaves, no branching and few flowers.
• In ideal conditions, grows up to 50cm tall with multiple branches, long, wide leaves (6cm x 2cm) and about 100 flowers.
• Leaves are generally 2–6cm long, alternate, dark green, with serrated margins.
• Flowers are bright yellow, daisy-like, with diameter of about 2cm, producing up to 100 seeds each.
• Each seed is 2–3mm long and cylindrical in shape, with rows of very fine short hairs and silky pappus (parachute).
• Taproot is shallow-branched with many fibrous roots.

• Seeds germinate in mild, warm conditions with light and moisture.
• Light infestations can produce 1 million seeds per hectare.

• Visit Weeds Australia and click on the distribution tab to access the distribution map.

• Seedlings appear March–June, growing quickly to produce first flowers in 6–10 weeks.
• Begins to dieback in spring.
• Dry summer followed by autumn or winter rains leads to heavy infestations.

Economic

• Competes with pasture species.
• Toxic to livestock, particularly cattle and horses, causing illness, slow growth and poor conditioning, which can result in death.
• May taint meat and milk.

• Seeds spread by wind, stock, in pasture seed, hay, turf, mulch and with stock transport.

• Find out how farmers can prevent weed spread.
• Find out how gardeners and outdoor enthusiasts can prevent weed spread.

Physical control

• Prevent establishment by ensuring dense cover of pasture in autumn and winter.
• Remove small infestations immediately.

Mechanical control

• Chip out, bag and burn isolated plants. Wear gloves when handling fireweed plants.
• Slashing is usually not effective, as it increases poisoning risk to stock and only delays flowering and seeding.
• Cultivation is not recommended.
• Fireweed remains toxic after being cut and becomes more attractive to stock.

Herbicide control

• Herbicides are most effective if sprayed before plants reach maturity. However, application during flowering will be effective if higher recommended rates of herbicide are applied.
• Research is ongoing for herbicide controls, including residual control methods. Trials have shown herbicide application in the autumn period during April provides good control. Before undertaking such programs, landholders are advised to determine infestation levels.
• Effective application method in an open pasture situation is a boom spray. Follow this up by spot spraying, or pulling and bagging any regrowth or missed plants.
• Boom spraying is also suitable for follow-up treatments, as it allows destruction of immature plants, which may otherwise grow to re-seed the area before they can be noticed.
• Bromoxynil (trade names Bromicide 200, Brominil 200 and Buctril 200) is suitable for use in pastures containing clovers, medics and lucerne, and will not affect grass.
• Bromoxynil is effective if used on seedlings, which usually appear in autumn and early winter but may appear later following rain. Twice as much bromoxynil is needed if it is applied to plants that are just beginning to flower. Bromoxynil is less effective on mature plants, as it is a contact herbicide only. Mature plants will only be killed off where the bromoxynil comes into contact with the plant, allowing recovery of the plant from lower, untouched portions.
• Conduct follow-up inspections every 4 months after initial treatment. Re-treat as required.
• Unfortunately, fireweed control is often not considered until the highly visible flowers appear and it is too late for effective control with herbicide.

Read the fireweed fact sheet (PDF, 2.1MB) for herbicide control and application rates.

Biological control

• Organisms can be found attacking fireweed, but any effect they have is temporary and isolated.
• Orange rust (Puccinia lagenophorae) is common and often affects fireweed, particularly in lower country.
• Blue stem borer moth (Patagoniodes farinari) is also common, but larvae usually develop too slowly to have an impact.
• Two moths imported from Madagascar have been host tested. In controlled tests they were found to feed on important non-target plants so no releases were made.
• Other potential biological control agents have been identified, but rigorous testing is needed to ensure that they do not feed on closely related Australian native plants. Investigations in South Africa are presently being undertaken.

• Fireweed is a category 3 restricted invasive plant under the Biosecurity Act 2014.
• It must not be given away, sold, or released into the environment. Penalties may apply.
• You must take all reasonable and practical measures to minimise the biosecurity risks associated with dealing with fireweed under your control. This is called a general biosecurity obligation (GBO).
• At a local level, each local government agency must have a biosecurity plan that covers invasive plants in its area. This plan may include actions to be taken on fireweed. Some of these actions may be required under local laws. Contact your local government for more information.