Dittrichia graveolens is in the Asteraceae family. It is native to the Mediterranean region of Europe. Stinkwort is erect, growing to 2.5 feet. It typically has a conical shape but can have a round appearance. It’s sometimes confused with Russian thistle (tumbleweed). It ﬂowers from September to December and produces tiny seeds. Stinkwort’s foliage has sticky hairs covered in resin that truly stinks and sticks to and stains skin.
Stinkwort was ﬁrst reported in Santa Clara County in 1984 and has increased at an exponential rate. It likes disturbed soil in urban areas and is in San Luis Obispo county. For example, in San Luis Obispo, there is a stand on California Blvd. near the corner of Foothill.
Due to its shallow root system stinkwort can be controlled by handpulling and bagging. It would be wise to wear protective clothing especially gloves. Stinkwort can cause contact dermatitis. Mowing, grazing or burning are not effective controls. In fact, stinkwort poisons livestock. There are no biocontrol agents. The most effective herbicide is likely aminopyralid with triclopyr (Capstone). A good time to spray is when the plants have emerged or are bolting, prior to ﬂowering. The earlier the better as the oils in mature foliage makes it harder to control with herbicide. Stinkwort was discussed at the most recent Weed Management Area meeting at the County Ag Commissioner’s ofﬁce.
DiTomaso, J.M., G.B. Kyser et al. 2013. Weed Control in Natural Areas in the Western United States. Weed Research and Information Center, University of California. 544 pp.
Brownsey R, Kyser G, DiTomaso J. 2013. Stinkwort is rapidly expanding its range in California. Calif Agr 67(2):110-115.
Image by Javier martin (Own work) [Public domain or Public domain], via Wikimedia Commons