Apparently a corruption of "buckwheat," a shrub (Eriogonum fasciculatum and other species) that is a major plant component of sage scrub and chaparral in Southern California. Currently (10-22-07) being used by the media to describe the Agua Dulce fire now raging in the Santa Clarita area north of Los Angeles. Local Los Angeles news media generally betray a total lack of knowledge of the native flora, having in the past described coastal fires in Malibu as "burning hundreds of acres of mesquite" --a plant that does not grow there. I am unable to come up with a place name called "Buckweed" and I am assuming that the so-called "so-called Buckweed Fire" is in fact based on a corruption of buckwheat. I'd be happy to learn otherwise.
"The so-called Buckweed Fire continues to rage out of control."