Perennial ragweed is a State prohibited weed
State prohibited weeds are the highest category of declared noxious weeds in Victoria. By definition, they are either not yet in Victoria, or are here in small numbers, where their eradication is still possible.
All sightings should be reported to Agriculture Victoria immediately by calling 136 186 or emailing firstname.lastname@example.org.
Why is it important to report perennial ragweed sightings to Agriculture Victoria?
Perennial ragweed is native to North America but now occurs on every continent, having spread widely in the past 150 years. Perennial ragweed does not currently occur in Victoria, after small infestations were eradicated in the 1960s. However, reintroduction from established NSW populations remains a threat.
Perennial ragweed is one of a suite of Ambrosia species globally recognised among the most problematic of invasive weeds. It thrives in disturbed environments, therefore placing urban and agricultural areas at risk.
It is a strongly competitive plant and dense infestations reduce crop and pasture production; it is both unpalatable to cattle and releases allelopathic compounds that inhibit the germination and growth of many plants, including a range of crops. Perennial ragweed also poses a seasonal public health concern due to its highly allergenic pollen.
How to identify perennial ragweed
Perennial ragweed is a large and erect perennial herb with a robust lateral root system.
It grows densely in human-disturbed environments, particularly in sandy soils.
Leaves are grey-green, with a glandular and hairy surface. They are lobed and occur on short stalks.
Male and female flowers occur on the same plant; male flowers are cream-coloured and are grouped together in 3 mm hemispherical cups with many gathered at the end of stems, while the singular female flowers occur in the axils of upper leaves.
Perennial ragweed reproduces mostly from new shoots that grow from the highly vigorous lateral roots. The plant even readily regenerates from root fragments. Therefore, soil movement can lead to wider dispersal and further infestation.
What should you do if you find perennial ragweed?
If you think you have seen perennial ragweed, please contact Agriculture Victoria on 136 186 or email email@example.com.
Please do not attempt to treat or dispose of this weed yourself. Agriculture Victoria will treat, remove and dispose of perennial ragweed safely, at no cost to the land owner.
In Australia, perennial ragweed was first recorded in NSW in 1922. It is unclear how it was introduced, although trade in grain contaminated with ragweed seed is likely. There is evidence that later introductions in coastal areas occurred through contaminated United States Army trucks brought over during World War II.