By Conservancy Stewardship Manager Laura Pavliscak
The sunny glow of the hillslope above Chanac Creek is far from a welcome site--flowering Saharan mustard densely infests this area and competes with native species.
The transition between late winter and early spring is a busy one for Conservancy staff as we prepare for guests and researchers seeking blooms, nests, and the miracle of vibrant spring biology. But long before the wildflower viewing and ranch tours are planned, Conservancy staff and volunteers are out laboring against our most nefarious invasive annual—Saharan mustard (Brassica tournefortii). While the winter rain promises verdant green wildlands, it also initiates opportunities for the well-adapted invasive plants that have taken hold in our open spaces, and Saharan mustard is an excellent example of a highly successful invader that has encroached across the open spaces of Tejon.
Clusters of showy red flowers reveals a rare population of California jewelflower surrounded by densely growing yellow-flowered Saharan mustard. This jewelflower is listed under both the Federal and State Endangered Species Acts as endangered and only a few populations are thought to exist. In 1 x 2 meter plots in this area where Saharan mustard plants were counted, almost 2500 individuals were encountered in one plot.
Invasive species can have a devastating impact on biodiversity and ecological function, and are implicated in directly contributing to the decline of over 40% of the threatened and endangered species in the United States. Saharan mustard is one of several invasive species on Tejon Ranch, but is one of our most concerning invasive plants, listed by the California Invasive Plant Council as highly invasive—their most severe ranking in impacting ecology at the state level.
Hard working and dedicated volunteer Paula Harvey, pulling Saharan mustard along Comanche Point.
From the northernmost boundary of the Ranch to Tejon Creek, Saharan mustard has steadily become a dominant presence in the San Joaquin Valley grasslands, out-competing native plants and thriving in areas with rare, arid adapted species like California jewelflower (Caulanthus californicus) and Comanche Point layia (Layia Leucopappa). It is incredibly resilient—going from seed to fruiting plant in as little as six weeks with new plants emerging with every meaningful pulse of rain. An individual plant can produce thousands of seeds. It is superbly adapted to arid climates and to responding quickly to available resources, and can disperse rapidly across an open landscape if it is transported by something relatively large and quick (aka cattle and vehicles). That is why we have been focusing on treating Saharan mustard along the major roads in the area and in the rangelands adjacent to our rare plant populations.
Saharan mustard growing densely along the sandy bottom of Tejon Creek. Mature individuals can range from a few inches to over 4 feet and produce very dense populations, excluding native species.
Starting in February we have removed hundreds of thousands of plants, clearing almost 6 miles of roadside, as well as treating the vicinity of a few areas of both the aforementioned rare plants. There is so much more work to be done in constraining this aggressive invasive, but for now the plants have dried up and removing them poses the danger of more broadly spreading the seed. While the treatment season is over this year, those who care about the unique plants special to Tejon as well as the complex ecology that is supported by a mosaic of diverse species rather than the dominance of one, are welcome to join us next winter as we continue the fight! Special thanks to volunteers Paula Harvey for her persistent roadwork along Comanche Point and Reema Hammad for helping document the spread.
Removing Saharan mustard by hand along the roadsides of Comanche Point with Paula Back-of-Steel Harvey, volunteer extraordinaire.