Dylan,

FHM are naturalized in CA in some locations. Although the map below probably doesn't document all of the locations, they are definitely occurring in areas intersecting the Sacramento River watershed. You can look at map where documented in the link below.

https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=621

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers