The Enemy: London rocket (Sisymbrium irio)
Strategy: This weed is an introduced plant from Europe. The plant was brought here as an herb that was used for cough and chest congestion and for cleaning wounds. Like all plants in the mustard family, the flower has four small yellow petals that occur atop the vegetative growth of the winter annual plant. Once the plant starts setting seeds the pods will align along the stem above the remaining leaves. Unique to this plant is that the flowers occur in round clusters but the center flowers don’t bloom at the same time as the outer flowers so it can appear in a large ring. The leaves are deeply lobed with a white midvein.
Attack: As this is a winter annual, it gets a jump start on desirable plants. Once established, it crowds out sunlight and outcompetes desirables for sunlight and water. It is aggressive and produces thousands of seeds that spread quickly. It can grow in any open-soil area, whether it be in the backyard or sagebrush areas. Like all mustards, this plant is generally not grazed by livestock.
Defense: Don’t allow this plant to spread. Pulling it is effective and cultivation on a large scale will kill it. When the plant is young, 2,4-D is effective, but once the plants become mature one must use products in the Sulfonyl urea family. These include products such as Harmony, Telar XP, Escort XP, Opensight and others. I am not an advocate of using Roundup as you remove many desirable plants and it is not effective against these types of weeds. Call your local weed professional for proper identification to ensure quality control of this weed.