The shrubby mayweed (Oncosiphon suffruticosum, Afrikaans: Knoppiesstinkkruid, "button stink herb") is native to Namibia and the Western Cape and Northern Cape provinces of South Africa. The species is listed on the SANBI Red List as "safe" (LC).
Shrubby mayweed is an annual plant with leaves that have an irritating smell. The flower consists of many yellow buttons around 5 mm in diameter. It grows knee-high and has feathery gray-green leaves. It grows in barren, sandy soils, such as the shores of salt marshes. In Australia, it is considered an invasive species.
In South Africa, it is a weed that can seriously challenge crops, due to its strong smell that repels most livestock and adversely affects the taste of milk and meat from animals that do consume it. Fortunately, it only propagates by direct seeding and therefore spreads slowly.