Brassica nigra, native to parts of Northern Africa and Eurasia, is thought to have shown up in the western U.S. in the 1700s. Today, it occupies tens of thousands of acres and outcompetes native grassland and chaparral species. The dried stalks of mustard plants are highly flammable and subject to wildfire and it is also a fire-follower, often proliferating in the wake of disturbances like fire.
