Those bright yellow puffballs showing up around the Valley this spring are not wildflowers doing you a favor. They are stinknet, and local officials along with conservation groups are urging homeowners to rip them out of yards before the plants set seed. Crush one and you get a sharp, turpentine-like odor. Let them dry out and they turn into dense mats that burn hot and fast. Residents are being warned to remove stinknet carefully, since the seeds are tiny and easily spread, and the dried plants can aggravate allergies and asthma.
According to 12News, municipal officials, including the City of Tempe, are asking Valley homeowners to help keep the weed from bouncing back. A single seed head can produce hundreds of seeds. Conservation groups quoted by the outlet urge people to bag plants immediately, seal the bags, and then toss them. Stopping stinknet before it flowers is the quickest way to keep a few plants from exploding into a full-on infestation.
What It Is And How To Spot It
Stinknet (Oncosiphon pilulifer), also known as globe chamomile, is a winter annual that has spread through Maricopa, Pinal, and Pima counties, according to the University of Arizona Cooperative Extension. The plant has finely divided, carrot-like leaves and round yellow flower heads, and the foliage smells strongly of turpentine when crushed. Extension materials note that a patch can shed thousands of seeds that stay viable in the soil for years, which is why land managers keep hammering on early removal, preferably before flowering.
Fire And Health Risks
The National Park Service and regional partners report that thick stands of dry stinknet create highly flammable drifts that burn hotter and travel farther than many native plants. Those fires produce caustic smoke that can irritate eyes and lungs. As the Valley heads into the dry season, that combination ramps up both wildfire danger and public health concerns. Park and land managers warn that once stinknet really takes hold, it becomes expensive and difficult to get under control.
How To Remove It Safely
The Central Arizona Conservation Alliance advises homeowners to kill or pull stinknet while it is still green and before it flowers. Protective gear matters: wear gloves and long sleeves, and dig up the entire plant, roots included. All removed material should go straight into sturdy bags that are sealed and placed in the trash. Do not compost it or leave piles sitting around where seed can shake loose. For big, established patches, the group recommends hiring a licensed applicator instead of trying large-scale mechanical removal on your own.
Report It And Join The Effort
Regional mapping and volunteer workdays are coordinated through projects such as stinknet.org, which collects sighting reports and connects volunteers to removal events run by partners like the Arizona-Sonora Desert Museum. If you spot a suspect plant, take a photo, pull what you can safely, and file a report so professionals can prioritize treatment. Local parks departments and extension offices also post removal events and how-to guidance during the February through April removal season.
If you see those yellow balls in your yard, pull them while they are green, bag them, and check your shoes and pets for hitchhiking seeds before heading inside. For identification help and step-by-step instructions, the University of Arizona Cooperative Extension offers detailed materials. Hoodline has also highlighted the plant's impact, including when an outbreak led to a weed shutdown of a Casa Grande Ruins picnic area.
