Grassland Burns Burning invasives Burning in late June to control for the still-flowering, invasive medusahead grass. June 2019, Humboldt County. Invasive medusahead seed heads post burn June 2019, Humboldt County Yellow star thistle and medusahead Burning in late May, the annual grasses had dried while the yellow star thistle and medusahead had yet to make mature seeds. Burning at the optimal phenology window can help reduce the regrowth of target invasives by up to 90%. May 2019, Sonoma County. Post Rx fire wildflower bloom The spring wildflower bloom after the above grassland burn. Native wildflowers such as Sky lupine, Popcorn flowers, Fiddlehead flowers and Meadowfoam were abundant and happy with the hard work. March 2020, Sonoma County.