kcweeds

Burning a Garden to Save a State

This is the success story of how a never before found parasitic plant species in North America was found and handled in Washington state.

Aside from sharing the story, please note that the King County Noxious Weeds Program was not directly involved. This story was made possible with the help of those who worked on the ground, namely Susan Bird with the Yakima County Noxious Weed Board and Greg Haubrich with the Washington State Department of Agriculture (WSDA). 

What it is
Potential impact
ID & Prevention
How it was handled
What’s next
Worker using a propane weed burner to burn a garden, houses and fields in the distance.
It takes a team! Containing this infestation to protect the community took tremendous effort that included at least 42 different entities.

In July 2025, a homeowner and grower in Yakima County, Washington noticed something unusual in her blueberry patch. Like many curious plant enthusiasts, she uploaded photos of the mystery plant to iNaturalist for help with identification. Within days of posting, scientists from around the world were writing in urging her to confirm the plant’s identity. For if it was what they suspected, it would mark the first recorded occurrence in North America of a highly concerning parasitic plant species.  

Screengrab from iNaturalist report of the Sunflower Broomrape found in Washington. Shows photo of the plant and a commenter saying "If so, it looks like a first record for Yakima County. Interesting find! Parasitic plants always amaze me"

Following recommendations from the iNaturalist community, she contacted the Washington State Department of Agriculture (WSDA) and the Washington State University (WSU) Extension Program. WSU then shared the report with the United States Department of Agriculture (USDA). All three organizations collected samples for genetic testing. 

Initially, the USDA was skeptical—there are several similar, non-threatening species in the region—and suggested waiting for the plant to mature for clearer identification. Unfortunately, this delay allowed the fast-growing plants enough time to go to seed. When test results returned, they confirmed the internet’s suspicions: 

This was the first documented North American occurrence of sunflower broomrape (Orobanche cumana), a potentially devastating parasitic plant if not caught in time.  

This is not a scary story, but an inspiring one—how a single, well-timed moment of curiosity unexpectedly brought a small problem to light before it could grow into something far more serious. By identifying the mystery plant in her garden, one landowner set in motion a chain of events that ultimately led to the prevention of a potentially world-altering pest. What followed was a coordinated response, strengthened by international support, enabling quick action to safeguard the livelihoods of many.  

Let’s get into the weeds! 

What is Sunflower Broomrape?

Sunflower broomrape (Orobanche cumana) is a parasitic plant that depends entirely on specific host plants to survive—often killing them in the process. As its name suggests, it primarily targets sunflowers. However, recent findings indicate it may also impact a broader range of plants, including nightshades (such as tomatoes and eggplants), tobacco, and wormwoods (such as sage and mugwort). 

A field of sunflowers showing some plants wilting and drying out, with healthy sunflowers in the background.
Wilting sunflowers with an abundance of sunflower broomrape growing at their base from an Argentinian article (in Spanish, see here) discussing the impacts of this species.

One of the most concerning aspects of this plant is its ability to spread. Within roughly two weeks of emerging from the soil, it can release thousands of tiny, dust-like seeds. These seeds can remain viable in the soil for 50 years or more.

8 steps of lifecycle drawn in colored pencil, illustrating what caption explains.
Lifecycle of sunflower broomrape (drawing by Anne Schuster – WA state noxious weeds). 1. Seeds in soil near sunflowers, 2 & 3.  host’s roots send stimulating chemicals that cue parasite germination, 4. parasite germinates on roots of host plant, 5. parasite emerges from soil/evidence of host plant distress, 6. parasite flowers, 7. parasite seeds spread/host plant dead, 8. dead stalks remain of both plants, cycle begins again. 

Once established, sunflower broomrape is extremely difficult to eradicate and can devastate entire fields. Any area where these seeds have been found nearby may require strict quarantine and extensive decontamination before it can be considered safe again. 

Map of Europe showing native and introduced plant species, with native areas highlighted in green and introduced areas in purple.
Until this discovery, sunflower broomrape had only been found in and around its native range (Southeeastern Europe, Central Asian, Black Sea, & Caucasus regions), and more recently in South America in 2021. See map source here.  

Local Impact Potential

The United States Department of Agriculture (USDA) is developing a Weed Risk Assessment document for sunflower broomrape. This assessment is what state and other entities like WSDA rely on for knowing how to address issues like this. Because it is novel to the continent the Weed Risk Assessment is still being drafted and not yet public, we will update this post with the link to the final report as soon as it is available.

Map of North America highlighting regions in light blue where Orobanche cumana is likely to become problematic, along with reported occurrences marked on the map.
Map from the USDA’s drafted Weed Risk Assessment of sunflower broomrape showing where the species is likely to become problematic if introduced. 
Anyone who grows sunflowers:

Eastern Washington alone has 9,000+ acres of commercially grown sunflowers. On average, each county in WA produces up to 5,000 metric tons of sunflower oil. Sunflowers are also commonly used in crop rotations by hay growers to replenish soil nutrients.

Growers of other host crops:

Crops such as tomatoes, eggplants, tobacco, and sage are also vulnerable. Infestations could result in total crop loss, long-term inability to grow these plants, and significant control costs once the parasite becomes established.

Those in quarantined areas:

Beyond growers, anyone moving soil or vegetation within a quarantined area could be affected. This could include strict limits or bans on transporting any plant material or soil in and out of affected zones and a ban on growing potential host plants within that zone.

Row of plants in a field with signs labeled 1, 2, and F1, showing variations in plant health, with some plants appearing wilted and others healthier.
Wilted sunflowers in a study (see image source here) on sunflower broomrape demonstrating the impact of the species.

How Can We Prevent It? 

Early detection is critical.  See it, report it.

The origin of this infestation remains unknown. Seeds can remain dormant in soil for decades and may activate when a suitable host is planted. If you grow sunflowers, tomatoes, tobacco, eggplants, or sage, monitor your plants closely—especially if you notice unusual decline or die-off. 

If you suspect sunflower broomrape: 

What to look for: 

  • Sudden wilting or yellowing in sunflower and other host plants  
  • Plants can only survive with appropriate host plants and grow at the base, closer to the roots of these plants only.
  • Pre-bloom stalks resemble yellow asparagus
  • Early flowers appear as yellow tubes that grow in a spray towards the top of each stem 
  • As flowers mature, they turn purple, stems remain yellow
  • As plants die, they brown and dry, flowers stay intact

Timing: in the PNW these plants typically germinate around June and can persist through August when their host plants (sunflowers, tomatoes, tobacco, sage) are growing.

Check out photos of this species in different stages of life here in iNaturalist.

  • Cluster of 20+ plants growing at the base between two sunflower stalks, each sunflower stalk is 3-5x wider than each broomrape plant.
    Growth location is key! These plants cannot survive without their preferred host plants, typically sunflowers. (PC: supporters from Krasnadoar Russia).
  • 5 plants growing amongst sage. Two are closed and look like yellow asparagus, 2 are open revealing tube like flowers.
    Early flowering stalks appear yellow and resemble asparagus before flowers open. PC: 5/23/23 post by svetlana-bogdanovich on iNaturalist.
  • Standalone mature flowering plant showing purple tube like flowers growing in a spray at top 2/3 of stalk.
    Plants do not have obvious leaves, as flowers mature (quickly) the yellow tube like petals turn purple, stem remains yellow. PC: 5/5/22 post by sapsan on iNaturalist.
  • Close up of top of plant spike held between thumb and forefinger, plant is same width as thumb.
    Plants are quite narrow and only grow 11 to 40 inches tall. PC: 8/12/20 post by savvaszafeiriou on iNaturalist.
  • ~10 dry and brown plants growing at the base of sunflowers, flowers browned but still in tact.
    At the end of their lifecycle, above ground portions of the plant brown and die back, releasing dust-like seeds from each flower tube. PC: 8/11/25 post by viktoriasergiichuk on iNaturalist.

How Was It Handled in Washington State? 

Because this was the first known occurrence in North America, response efforts required rapid coordination and international guidance. Within months the community came together in an act of solidarity to protect local resources. At least 42 entities collaborated to contain the infestation. The effort was primarily funded by the WSDA, with significant support from partners including the Yakima County Noxious Weed Board and WSU. Thus far, efforts have cost upwards of $40,000, this number does not include many unaccounted labor costs, compensation for the landowner’s losses, or projected future expenses. This is a low sum relative to what it would have cost if caught any later.

On October 1st, 2025—three months after the initial discovery—WSDA issued a press release (see here) alerting the public. By October 21st, sunflower broomrape was designated an emergency Class A Noxious Weed, allowing an eradication process/treatment to take place, increased awareness, and a quarantine of the site and surrounding areas to be initiated. Eradication efforts began in October 2025 and are ongoing. An emergency quarantine was put into place on April 2nd, 2026 and a permanent one will be finalized by July 31st, 2026.

A two-part response plan was implemented simultaneously: outreach and containment. 

Part 1: Outreach

Educational materials were quickly developed, and more than 2,000 letters were sent to residents within a one-mile radius of the infestation site. Staff conducted door-to-door visits, speaking with neighbors, inspecting properties, and checking any sunflowers or plant remnants. 

They also contacted nurseries and suppliers connected to the homeowner to identify any potential source of contamination. Fortunately, no additional infestations were found. 

Outreach efforts remain ongoing. 

Part 1: Containment & Decontamination

This was the first time in North American history that a group had to work to eradicate sunflower broomrape, and while it proved no easy feat, they made it happen. With guidance from international partners who bolstered experience with the parasitic plant, and physical support from an array of community groups, the infestation was managed in a multi-step process. 

To start, a 100-by-100-foot area centered on the infestation site was designated for intensive decontamination. The situation was especially difficult because the landowner had recently launched a flower-cutting business. The affected zone included a hoop house, large potted plants, mature fruiting bushes, and garden beds. Due to the nature of seed dispersal, all exposed materials were considered contaminated. 

A group of people in white protective clothing working to extinguish a small fire on a hillside with a building in the background, surrounded by smoke and burnt vegetation.
A group of people in protective gear working in a rural area with smoke in the background, surrounded by hills and trees. They appear to be engaged in land management or cleanup efforts.

Workers were required to wear three layers of Tyvek protective clothing and booties to prevent possible offsite seed movement. All vegetation within the area was cut and burned using a trailer provided by the City of Pasco, a large burn atop the infestation site, and propane weed torches to burn any remaining open ground within the hot zone. The infestation burn was maintained throughout the day, reaching temperatures of at least 150°F for over 15 minutes to destroy seeds, with the fire department on-site for safety and to cool the burn at the end of the day.

Before and after brush was cut & burned (move slider in center to reveal either image).

Salvageable nursery supplies—valued at over $4,000—were cleaned and stored in a sanitized and sealed hoop house for further treatment. Non-cleanable materials like weed barriers, irrigation, and Tyvek (15, 55-gallon contractor bags in total) were transported in an enclosed U-Haul to an asbestos disposal facility, where proper handling was verified and the transport vehicle was sanitized

A person stands next to stacked black planting pots and crates in a garden area, with a blue tub in the foreground and a greenhouse in the background under a clear sky.
A person with long hair and a hat walking on a grassy hillside covered with straw and blue material, surrounded by a rural landscape with trees and houses in the background under a clear sky.

The following day, both the treatment area and a surrounding buffer zone (140 by 140 feet) were covered with four inches of pine shavings and treated with the highest effective rate of the herbicide aminopyralid to suppress host plants (sunflower broomrape will not germinate without potential host plants present). 

After the treatment window, the site was sealed with a 6-millimeter-thick solarizing plastic. A 3-foot plastic barrier was installed around the perimeter to prevent access by people and animals. In the winter additional weight of railroad ties and pallets were added to the plastic to prevent winter winds from disturbing the solarization process. 

A view of a large covered area on a hillside, with trees and a vineyard in the background, depicting autumn colors and a cloudy sky.

In spring 2026, thermometers were installed under the solarizing plastic to monitor soil temperatures, with the goal of reaching 150°F to kill any remaining seeds. The site will continue to be monitored, with the hope that it can eventually be safely reused. 

What’s Next? 

Efforts are ongoing and include: 

  • Emergency quarantine zone (1/4 mile radius from infestation site) established April 2nd, 2026. This puts temporarily rules into effect in a quarter-mile radius surrounding the site and allows WSDA access to their emergency funding to fund the ongoing efforts and work to prevent potential spread of this plant from the local area. WSDA has 120 days (until July 31st, 2026) to take the necessary actions to finalize a permanent quarantine, they sent postcards and letters to everyone in the impacted zone and will continue to work with them to form the final language. See the emergency ruling here: Washington State Department of Agriculture.
Map showing the Sunflower Broomrape Quarantine area in Yakima, WA, with highlighted quarantine zone, local roads, and nearby highways.
  • Continued monitoring of the site and surrounding areas  
  • Additional soil heating if solarization does not reach target temperatures (potentially using WSU steam equipment, pending funding).
  • Planting of germination stimulating crops that don’t serve as effective hosts such as sorghum or corn to encourage seed bank depletion. 
  • Expanded outreach and education statewide.

This success wouldn’t be possible without community 

Discovering and (hopefully) eradicating a potentially world-altering parasitic plant in less than a year is no easy feat. It takes the awareness and support of passionate community members, local organizations, and caring neighbors for a situation like this to succeed. In the world of weeds, things can sometimes feel insurmountable. While the work continues, this success story is just one of many worth celebrating. So, thank you to everyone who made this happen—and thank you for taking the time to read this story of curiosity, collaboration, and containment.  

Happy Weeding! 

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