The answer, according to botanists and environmental agencies, lies inland. The tumbleweeds blanketing parts of Mission Bay are almost certainly Russian thistle, an invasive plant species belonging to the Salsola genus, most commonly Salsola tragus or Salsola ryanii. Despite being culturally synonymous with the American West, Russian thistle is not native to California. It thrives in dry, disturbed soils, grows rapidly during wet seasons, then dries out, snaps at the base, and quite literally tumbles across the landscape, dispersing seeds as it goes.
Southern California’s recent weather created the perfect conditions for this annual cycle to play out on a dramatic scale. Heavy rainfall during the winter storm fueled robust plant growth inland and along open corridors, followed by drying winds and runoff that transported the brittle plants downhill. In coastal zones like Mission Bay, those tumbleweeds are then carried by stormwater, wind, and tidal movement until they accumulate along beaches, paths, and shoreline infrastructure, often becoming tangled with seaweed, trash, and other debris.
While visually striking, the tumbleweeds are more nuisance than emergency. Russian thistle is not toxic, but it is invasive and highly efficient at spreading. Large accumulations can obstruct walking and biking paths, clog storm drain outfalls, and create localized fire hazards once fully dried. In coastal areas, they also contribute to the broader issue of debris management, as stormwater in San Diego flows untreated into the bay and ocean, carrying whatever it picks up along the way.
City crews periodically remove the tumbleweeds as part of routine storm response and shoreline maintenance, though the scale of accumulation after major storms can make cleanup feel slow or incomplete. Environmental officials stress that these events are seasonal and weather-driven, not the result of dumping or neglect, and tend to resolve once conditions stabilize and cleanup cycles catch up.
SanDiegoVille has reached out to multiple City of San Diego departments, including City of San Diego Stormwater Department, Parks & Recreation Department (Mission Bay Park), Environmental Services Department, and City of San Diego Public Utilities Department (Stormwater Division), for additional information on cleanup efforts, long-term management of invasive plant debris, and whether this winter’s accumulation is considered above average.
City crews periodically remove the tumbleweeds as part of routine storm response and shoreline maintenance, though the scale of accumulation after major storms can make cleanup feel slow or incomplete. Environmental officials stress that these events are seasonal and weather-driven, not the result of dumping or neglect, and tend to resolve once conditions stabilize and cleanup cycles catch up.
SanDiegoVille has reached out to multiple City of San Diego departments, including City of San Diego Stormwater Department, Parks & Recreation Department (Mission Bay Park), Environmental Services Department, and City of San Diego Public Utilities Department (Stormwater Division), for additional information on cleanup efforts, long-term management of invasive plant debris, and whether this winter’s accumulation is considered above average.
Originally published on January 6, 2026.
