It almost appears as if the trailhead to Lassen Peak was airbrushed with crimson in this photograph by Shanda Ochs, taken yesterday afternoon.
The color, in fact, comes from Davis Knotweed (Aconogonon davisiae). There are 27 varieties of knotweed native to California. Douglas knotweed grows in Lassen Volcanic National Park at this elevation.
Shanda said, “It was spectacular with the fog which made the color pop!” The dusting of frost on the volcano adds to the photo’s drama.
Notice the golden-orange ground cover near the base of the trailhead. The source of that color remains unidentified. Though, Fall Color creds go to the first person to comment and identify it. 
Lassen Peak Trail, Lassen Volcanic National Park (8,200′) – Peak (75-100%) GO NOW! – Davis Knotweed
Thank you so much for all this great information. This website is exactly what I’ve been looking for to find out where to go to see fall colors. And the map is fantastic!
Thanks. Great hearing from you, Sarah. Happy travels.