Stinknet (Oncosiphon pilulifer)
Stinknet, an invasive African annual weed that crowds out native plants and becomes a fire hazard in summer, currently spreading in Maricopa, Pinal, and Pima counties. Stinknet, sometimes also known as globe chamomile, is a member of the sunflower family. It can grow more than 2 feet tall and is spreading in Arizona as well as California, Nevada, Australia, and Mexico. The plant grows during winter.
Stinknet has finely dissected carrot-like leaves. Bright yellow spherical yellow flower heads, each consisting of many tiny flowers. Crushed foliage has a pungent, turpentine-like odor. The weed expansion threatens Pima County (Tucson) and surrounding counties in southern Arizona, where it has not yet invaded. It can occupy most habitat types. It is invading natural areas, neighborhoods, and everywhere in between. This species and other invasive weeds fuel wildfires, allowing wildfires to occur more frequently and with greater magnitude.
Noxious Weed Status: Stinknet is listed as an Arizona State Noxious Weed, Class B.
Identification
- Size: 2 inches up to 2+ feet
- Growth Form: Forb
- Leaves: Finely dissected (carrot-like)
- Odor: Crushed foliage produces a pungent turpentine-like stink. Flowering plants may emit this odor without disturbance.
- Flower heads: globe/spherical shaped, bright yellow, with many tiny flowers.
- Seed heads are globe/spherical shaped and brownish-tan colored. They consist of tiny individual flowers that have dried out, with a little mature seed at the base of each dried flower.
The Regional Stinknet Planning Team has developed a comprehensive Land Managers Guide to effectively treating and managing Stinknet Comprehensive Land Managers Guide to Manage Stinknet:
Additional Land Manager and Ecologist Guides:
Stinknet / UC Statewide IPM Program (UC IPM) (ucanr.edu)
Natural Area Pests: Stinknet (ucanr.edu)
Residential and Homeowners Guides:
Stinknet: a Weed Advancing in Southern Arizona
And the UA Webpage Stinknet Invasion | Cooperative Extension | The University of Arizona
The Arizona Native Plant Society Trifold Brochure
Photos by Juanita Armstrong