Plant of the Month: Stinkwort
Since nursery sales are paused for the summer, we are taking a break from our native plant blog series to talk about a non-native plant: stinkwort (Dittrichia graveolens).
All About Stinkwort
Young stinkwort plant (Photo credit: Petra Boester, taken at McClellan Ranch Nature Preserve)
Stinkwort (Dittrichia graveolens) is recognizable by its strong odor and sticky texture. However, the structure and coloring of the plant helps it blend in with some California native species such as hayfield tarweed. The leaves and stems of stinkwort are coated with small drops of resin, which emit the pungent aroma characteristic of stinkwort. Stinkwort grows in a shrublike form and can reach heights of up to 3 feet.
Native to the Mediterranean region of Europe and extending as far east as Turkey, Afghanistan and Pakistan, stinkwort was introduced to Santa Clara County in 1984. Since then, it has spread throughout California. The plant thrives in disturbed areas such as roadsides, overgrazed pastures and other environments where the soil has been disrupted. Its adaptability to such conditions has facilitated its spread, particularly in regions with climates similar to its native Mediterranean habitat, such as California. Stinkwort produces small yellow flowers in late fall and seeds from September to December.
Why and How to Remove Stinkwort
Stinkwort flowers in bloom (Photo credit: Dash Ridolfi-Starr)
Given the right conditions, stinkwort can outcompete and displace many of the California native plants that local insects and other animals depend on. Stinkwort itself is not palatable to most animals and can damage the digestive tracts of grazing livestock. Due to those factors, it’s important to reduce the presence of stinkwort in California.
When it comes to stinkwort, timing is key for its removal. Targeting the pre-bloom stage, typically in late spring to early summer, makes for easy removal. This is when the plant has grown but hasn't yet started flowering. Removing stinkwort before it flowers prevents it from producing seeds and spreading further. Hand pulling or mowing is an effective way to manually remove stinkwort. Due to its sticky resin and strong odor, it is recommended to wear gloves when pulling stinkwort. Plants that have begun to flower should be bagged and disposed of after removal to prevent further seeding.
How You Can Help
Grassroots Ecology staff begin searching for and documenting stinkwort in July or August each year. But we rely on the help of volunteers to manage these populations. Join us for a volunteer day at Pearson-Arastradero Preserve, Foothills Nature Preserve, or Byrne Preserve to remove stinkwort and other late-summer weeds.
If stinkwort is present on your property, we advise removing it either by manually pulling it out or by mowing it down before it has a chance to bloom, then replacing it with native plants. Introducing native plants enhances the biodiversity of the plant community, thereby enriching the diversity of insects and animals that live in that ecosystem.
Stinkwort thrives in disturbed habitats, such as roadsides
By Petra Boester, Watershed Stewards Program Corpsmember
