Sisymbrium loeselii is a species of flowering plant in the mustard family known by several common names, including small tumbleweed mustard, false London-rocket, and tall hedge mustard. It is native to Eurasia, and it is known on other continents as an introduced species and in some areas a common roadside weed. It is an annual herb producing a hairy, erect stem which can exceed a meter in height. The leaf blades are divided into triangular, lance-shaped, and toothed linear lobes, and are borne on petioles. The top of the stem is occupied by a raceme of flowers with bright yellow petals each measuring just under a centimeter long. The fruit is a silique up to 3.5 centimeters in length containing tiny seeds.