Fireweed (Senecio madagascarensis) is a bright yellow-flowering, daisy-like weed that looks a bit like a cross between the common garden wedelia and a dandelion. But don’t be fooled by the cheery appearance: this plant is invasive, and it’s highly toxic to livestock.
Fireweed, also known as ragwort, invades pastures, roadsides, and disturbed areas. The plant contains toxic chemicals called pyrrizolidine alkaloids, which are poisonous if eaten by horses, cattle, and other livestock — causing liver damage, poor appetite, failure to thrive, weight loss, and even death. Horses are especially sensitive to the harmful effects.
This plant’s yellow flowers mature into round, white thistle balls containing hundreds of tiny seeds – up to 30,000 seeds per plant per year – which blow in the wind for miles and are easily spread on boots, hooves or fur. Native to Madagascar and South Africa, ragwort/fireweed is a serious agricultural pest in Australia and has spread widely in Hawaii, on Mauai, Lanai, Oahu, and Hawaii islands. It was introduced to Kauai in the last decade at two hydro-mulching roadside areas.
Fortunately, it was detected early and became the target of intense eradication efforts by KISC and HDOT. And the good news is . . .
Fireweed is a success story for Kauai! Early detection and rapid response were successful in arresting the spread of this dangerous weed, and it has been eradicated from our island. For the sake of our pasture animals, we constantly monitor for signs of its return.
You can help! Take a moment to become familiar with the difference in appearance between common garden wedelia and the highly invasive Fireweed that we need to watch out for:
Fireweed is a KISC target and is on the Hawaii State Noxious Weed List. If you suspect you have seen fireweed on Kauai, please report it: 643-PEST or 808-821-1490 / kisc@hawaii.edu. Take a photo if you can. Mahalo!
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