Stockton’s downtown waterfront faces an annual takeover by invasive water hyacinth, a fast-growing plant that can blanket thousands of square feet of water in a single season.
Deemed “hopeless” by PBS in 2015, the plant returns each year to San Joaquin County waterways, including McLeod Lake in Stockton,the Calaveras River and the broader Sacramento-San Joaquin Delta. Known as “the fastest-growing plant in the world,” a single hyacinth can wreak massive ecological and economic damage, making it one of California’s most destructive invasive species.
Unlike other invasive plants, experts say eradication is nearly impossible, leaving ongoing control as the only viable solution. For decades, the invasion of water hyacinth and other invasive plants like alligator weed have been a persistent problem for Stockton.
In March, California State Parks’ Division of Boating and Waterways (DBW) began treatments on hyacinth and other invasive plants in the Sacramento-San Joaquin Delta. According to a press release from the state, DBW treated more than 3,500 acres of floating and submerged aquatic vegetation last year, using various herbicides and mechanical methods.
Deputy Port Director Jeff Wingfield said the Port of Stockton isn’t currently seeing large amounts of hyacinth, as it’s isolated to downtown and the San Joaquin river, though past blooms have been intense.
“I’ve seen years where we’ve had almost no hyacinth and years where we’ve had so much that it looks like you could walk across the channel,” Wingfield said.
The Port of Stockton is California’s most-inland deepwater sea port that mainly handles bulk goods like cement and grain instead of big container ships. Its smaller cargo vessels can run into problems when hyacinth fills the waterway.
Wingfield said hyacinth can interfere with ships, especially at night when crews rely on radar.
“If you have big mats of hyacinth out there, it makes radar pretty much useless,” Wingfield said.
The sudden growth of hyacinth in the Stockton waterfront and port area is normal considering the recent rains that push it down the Sacramento-San Joaquin Delta.
“I’m hopeful that we’re just seeing this first flush and that we’re not going to see more after this,” Wingfield said. “Every year is kind of different.”
Wingfield said hyacinth tends to go dormant when temperatures drop to about 40 degrees and the plant freezes. However, it bounces back once the weather warms up, creating a constant cycle that keeps crews having to tackle it again and again.
Stockton Marina Director of Operations Chris Magro said hyacinth hasn’t affected boating in the marina for several years. He referenced past photos online from 2018-2020 that show the hyacinth growing past the docks and along the marina.
“We have not seen it at all in the last five years or so, and then in two weeks a whole lot of them showed up,” Magro said. “It’s up by Center Street, but the boats don’t go up there.”
Hyacinth accumulated in the waterfront along Center Street, including McLeod Lake, DeCarli Plaza and the Joan Darrah Promenade last month. However, it didn’t grow past the Weber Points Event Center. The overgrowth has since been cleared out of the downtown waterfront.
Stockton Public Information Officer Tony Mannor said the city purchased a workboat to clean up invasive plants and debris in McLeod Lake and the Stockton Channel surrounding the downtown marina in September 2022. Since April of last year, the Magnolia has been operated weekdays by a two-person crew from the city of Stockton’s Municipal Utilities Department as part of the McLeod Lake Cleanup Program, according to Mannor.
The city initiative aims to keep the downtown waterfront clean by using a workboat to remove floating trash, aquatic weeds and debris from the lake and nearby channels. The program also supports research studies, like dye-tracing to understand and reduce harmful algae blooms in the area.
“Since its launch, the Magnolia has removed approximately 35 tons of trash and debris from McLeod Lake and the Stockton Channel surrounding the downtown marina,” Mannor said.
Tidal shifts last month carried a large amount of hyacinth into the waterfront, he said, with the volume exceeding the Magnolia’s capacity.
“The inundation of hyacinth was so extensive that it prevented safe operations for the crew and vessel,” Mannor added.
DBW leads efforts to manage invasive aquatic plants in the Delta, Mannor said, though local results have not been effective.
“Despite this state designation, limited funding and program inefficiencies have resulted in minimal benefit to local waterways,” Mannor said.
“Under the city’s McLeod Lake Program, the budgeted daily cleanup operation costs of the Magnolia and crew are approximately $240,000 each year,” Mannor said.
Hyacinth cleanups take place periodically and may involve funding and participation from multiple agencies, he said, expenses of which include labor, equipment, maintenance and fuel.
Kevin Murphy, public information officer for California State Parks, said aquatic vegetation control in Stockton and nearby areas is guided by public reports, agency input and regular DBW surveys, with control efforts in the Delta determined annually.
“One resident, San Joaquin County and the City of Stockton have made reports about the presence of water hyacinth in McLeod Lake,” Murphy said.
Water released from headwater reservoirs, such as the Shasta Dam and New Hogan Reservoir, is moving vegetation downstream quicker than anticipated, Murphy said. And this year’s warmer weather has allowed the hyacinth to stick around longer.
“Upstream reservoirs have increased water releases from 14,000 cubic feet per second in June to 46,000 in late October,” Murphy said. “Warmer weather has also allowed plant growth to continue later into the year.”
Invasive aquatic plants lack natural controls in the Delta, Murphy said, where they displace native species vital to biodiversity and harm the region’s economy, environment and public health. Warm temperatures accelerate their growth, he added, forming dense mats that endanger boaters and block waterways and irrigation systems.
“Due to their ability to spread rapidly to new areas, the plants will likely never be eradicated from Delta waters,” Murphy said. “Therefore, DBW operates control programs as opposed to eradication programs.”
Treatment is ongoing as DBW monitors the spread of water hyacinth and follows a designated treatment plan, Murphy said.
“As recently as this week, we continue to treat vegetation in and around Stockton and will monitor its movements and decay,” Murphy said.
Want more? Sign up to get Stocktonia delivered to your inbox three days a week.