Chromolaena odorata (Devil Weed) is a Noxious Weed native to North, Central, and South America. It is one of the world’s worst 100 invasive species and has scored high risk on the Hawaii-Pacific Weed Risk Assessment.
Sometimes described as the ‘perfect weed,’ (devil weed sometimes written as devilweed), reaches reproductive maturity in as little as 6 months. Each plant can generate as many as 800,000 seeds!
The lightweight seeds are easily windborne, spreading up to 250 feet from the parent plant. By far, the greatest spread is by humans through the accidental movement of seed. Contaminated tools, shoes, clothes, fur, hair can all contribute to seed movement. Seeds remain dormant yet viable in the soil for more than a year. Devil weed reproduces vegetatively from the crown buds, stem pieces, and root fragments.
It thrives in full sun, both in disturbed and natural areas. Devil weed is a serious threat to agriculture, taking over pastures and aggressively outcompeting other plants. The nutrient-demanding plant will form monospecific stands that impede the growth of other species. And the allelopathic properties ensure nothing living can survive within Devil’s weeds range.
It is deadly to browsing animals. In the Philippines, 3000 cattle die annually from devil’s weed poisoning. It causes severe allergies and skin problems for humans.
On Hawaii Island
Devil weed was found on the Big Island for the first time in 2021, growing at the dragstrip and motocross area of Hilo, and just beginning to spread into nearby agricultural fields. This is no surprise, considering it was previously found growing on a motocross track on Oahu. The small, sticky seeds were likely transported by accident from Oahu, potentially on clothing, equipment, gear or off-road recreational vehicles. If you use the motocross and drag strip area, it could easily have hitched a ride home with you!
If found, please report to the Big Island Invasive Species Committee (BIISC). Early detection of new populations is crucial to island-wide eradication.
First detected in 2011 at the Kahuku Training Area, devil weed is now found in Kahana Valley, Pūpūkea, and most recently in ’Aiea (2015). Kahuku Training Area is also the weekend home of the Kahuku Motocross Track, popular with motocross and dirt bike enthusiasts as well as hunters. Vigilant decontamination of bikes, clothing, equipment, and gear after use is strongly encouraged, to prevent devilweed from spreading across O’ahu and potentially being accidentally transported to other islands.
- Herb or shrub with long rambling branches
- Leaves are triangular-shaped, opposite, with a toothed leaf edge. Leaves are also limp with velvety hair and have a distinct turpentine smell when crushed.
- The leaves have three thick veins shaped like a pitchfork, hence the common name “devil weed.”
- Flowers are held in small clusters—pale purple to off-white, usually with distinct long stamens.
- Fruits are tiny and have soft white hairs, which allow them to be spread on the wind or water. The hairs also act like Velcro, attaching themselves to anything passing by.
- For a more detailed description, click here.