Tall Hedge Mustard / Sisymbrium loeselii

Unfortunately, there are a lot of these plants growing along the Bow River, in the Pine Creek Water Treatment Plant area. Seen on a walk in the area on 3 June 2014.

"Sisymbrium loeselii is a species of flowering plant in the mustard family known by several common names, including small tumbleweed mustard, tall hedge mustard, and false London rocket. 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. This plant is allelopathic against other species growing around it - it produces chemicals that inhibit the germination of seeds of other species." From Wikipedia.

en.wikipedia.org/wiki/Sisymbrium_loeselii