If you have hiked around Phoenix in late winter or early spring, you have probably seen it. Rolling hills blanketed in tiny yellow button-like flowers. At first glance, it looks like a super bloom. It looks cheerful. It looks like spring.

It is not a native wildflower. It is stinknet, and it is rapidly transforming the Sonoran Desert.

Stinknet, officially known as Oncosiphon piluliferum, is an invasive annual plant native to South Africa. It is also called globe chamomile because of its small round yellow flowers.

Crush it in your hand and you will quickly understand the name. It releases a strong, unpleasant odor that many hikers describe as chemical or medicinal.

Despite its bright blooms, this plant does not belong in Arizona’s desert ecosystem.

Like many invasive species, stinknet likely arrived accidentally. It is believed to have entered the United States in the 1980s, possibly through contaminated seed mixes, nursery stock, or soil shipments.

Once introduced, it found perfect conditions in the low desert.

The Phoenix metro area provided everything it needed:

Each plant can produce thousands of seeds. Those seeds spread by wind, vehicles, shoes, pets, and stormwater runoff. Once established, stinknet moves fast.

Today, it is widespread across Maricopa County, Pinal County, and much of southern Arizona.

The biggest issue with stinknet is not how it looks in February. It is what happens in May and June.

The Sonoran Desert historically does not burn often. Native plants are spaced far apart, and there is not continuous fuel to carry large fires.

Stinknet changes that.

When it dries out, it forms dense, connected carpets of fine fuel. That creates a continuous path for fire to travel across desert landscapes that evolved without frequent wildfires. This threatens:

Fire in the low desert can permanently alter the ecosystem.

During a good rain year, we love seeing desert lupine, poppies, and owl clover. But stinknet competes aggressively with native annuals.

It germinates quickly, grows densely, and monopolizes sunlight and soil moisture. In heavy infestations, it can completely dominate an area, reducing biodiversity and limiting food sources for pollinators and wildlife.

That beautiful yellow blanket often means fewer native species underneath.

Part of what makes hiking in Phoenix special is the open spacing of the Sonoran Desert. You can see the shape of the land. You can see the saguaros rising above creosote and brittlebush.

Stinknet creates uniform, dense coverage that visually and ecologically changes that experience. It may look like a wildflower field, but it is a monoculture.

In the Phoenix area, stinknet is especially common:

If you see a mass of small, perfectly round yellow buttons covering the ground rather than distinct individual flowers, it is likely stinknet.

Land managers and volunteer groups work hard to remove stinknet, but it is a massive challenge.

If you encounter a small, isolated patch and are able to pull it before it goes to seed, that can help. The key is removal before seed production. Large infestations are best left to organized efforts, as disturbing them improperly can actually spread seeds.

Most importantly:

Prevention is far easier than eradication.

Stinknet is a perfect example of how something that looks harmless or even beautiful can quietly reshape an ecosystem.

The next time you see a hillside glowing yellow in the Phoenix desert, take a closer look. Not every bloom is a blessing.

Protecting the Sonoran Desert means understanding the difference.