Background
Syrian bean-caper is native to southwest Asia: the Syrian Desert, Armenia, Caucasus, northern Iraq, northwest and central Iran, and Turkey. Washington findings occurred in Grant County, 1916; in Yakima County, 1941; and in Lincoln County, 1964. Currently, populations grow in Adams, Grant, and Okanogan counties. In Idaho, it was collected at Minidoka in 1934; it currently grows near Aberdeen in Bingham County. In California, earlier reports placed Syrian bean-caper in 11 counties, but all infestations have been eradicated.
Syrian bean-caper may have been a contaminant in alfalfa seed from Turkestan when it was introduced in California in 1931. All the infestations in Washington appear to have started as ornamental or garden plants that have persisted in abandoned gardens from the homestead era. Settlers used flower buds as a substitute for capers. Spread from the former gardens was slow until the sites were mechanically disturbed.