Stinkwort Success

'Tis the end of fall, and for Open Space Authority volunteer Land Stewards and staff, the end of stinkwort season! This year, staff and volunteers saw a surprising reduction in the amount of stinkwort at Spreckels Hill and wetland area, located at the southern-most end of the Laguna Seca wetland in mid-Coyote Valley. This is evidence that long-term, consistent efforts to remove invasive plants can yield rewards for ecological restoration.  

Stinkwort, named for its strong Pine-Sol-like odor, is a relatively recent invasive plant in Santa Clara County. It is a Christmas tree-shaped, annual with a sticky resin that takes over grassland and seasonal wetland areas, especially in areas that have been disturbed by fire, roads, over-grazing and development. It’s also toxic to all grazing animals which means the Open Space Authority must find alternative methods for its removal, an essential step to restoring the land.  

There were multiple causes for this recent success at Spreckels Hill. In prior years, a pipe quickly drained the wetland into Fisher Creek, creating ideal conditions for stinkwort seeds to sprout. But this year, a newly-installed weir moderated the water levels, keeping the wetland full of water for longer and making it difficult for stinkwort seeds to germinate. Open Space Authority staff members also mowed the stinkwort in the uplands before its flowering period in late September and October of 2023. Thanks in part to these efforts, when staff surveyed the wetland in late summer of this year, there were no new stinkwort sprouts! Volunteers also played a tremendous role in the removal of stinkwort. 

Since 2021, concerted hand-removal efforts from staff, public and corporate Land Steward volunteers made a huge impact by cutting down on the viable seedbank remaining year after year. Land Steward volunteers from the public and various corporate and community partners such as Advantest, Starlight Community Services, the Project Management Institute and the Jewish Youth Climate Movement of Silicon Valley dedicated 400 hours of work to reduce, contain and nearly eliminate this invasive plant from the areas in and around Spreckels Hill.

In one day alone, volunteers removed 70 contractor bags of flowering stinkwort from the wetland. Over these last four years, staff and volunteers have effectively reduced the amount of stinkwort from 12 acres to less than one acre!

Removing all that stinkwort allows the Open Space Authority to use conservation grazing which reduce more (and less toxic) invasive grasses and thistles, thus improving habitat for native plants and wildlife. Due to the success at Spreckels Hill, Open Space Authority staff and volunteers will now pivot its focus to stinkwort populations on other protected lands throughout Coyote Valley. If you’d like to join in on the fun next year, please consider signing up to become a Land Steward volunteer!