Ambrosia pumila is a rare species of ragweed known by the common names dwarf burr ragweed and San Diego ambrosia. It is native to far southern California and Baja California where it grows in floodplains and scrub. Today it is known from 19 populations. Fourteen of them are in San Diego County, two exist in Riverside County, and there are three south of the border in Mexico. Most of its native habitat has been consumed by...
