What is fireweed?
This seemingly pretty plant is a serious weed that is poisonous and can be fatal to livestock. This weed invades overgrazed or drought ridden pastures and is often found along roadsides.
Why the threat?
When ingested, fireweed is toxic to cattle, horses, and other livestock, resulting in damage to the liver and neurological system eventually leading to death. Symptoms may occur after weeks or months of grazing, with irreversible damage.
How do you recognize fireweed?
The most recognizable feature of this weed is its bright yellow, daisy-like flowers. Each flower, 3/8" to 1" in diameter, has 13 petals. As the flowers mature, they turn into white thistle-balls.
What can you do?
Sightings of this weed on any island except the Big Island should be reported to the nearest office of the Hawaii Department of Agriculture or the Cooperative Extension Service, Tropical Agriculture and Human Resources, University of Hawaii.
Fireweed is not known to occur on the islands of Oahu, Molokai, Lanai, Niihau, and Kahoolawe.
Where are known infestations?
Native to Africa, fireweed was first discovered in the early 1980s on the island of Hawaii. Today, fireweed can be found from Kohala to Waimea, and in Kau.
In 1990, the weed was found along the roadway near Halfway Bridge, between Lihue and Koloa on the island of Kauai. This infestation probably started with some roadside plantings of grass seeds from Australia that contained some unwanted fireweed seeds. The Hawaii Department of Agriculture is working to eradicate fireweed from the Garden Isle.
On Maui, fireweed was sighted along the Pukalani bypass in 1997. The infestation is believed to have started with plantings of contaminated grass seeds used to beautify new roadways. Now, fireweed can be found from Kapakalua-Haiku to Pukalani.
This publication is produced by the Plant Pest Control Branch, Division of Plant Industry, Hawaii Department of Agriculture
P.O. Box 22159 Honolulu, HI 96823-2159