Semi-desert, foothills. Disturbed areas. Spring, summer.
Hawkins Preserve, Cortez, Colorado, May 23, 2006.

This native of Europe has spread aggressively throughout the United States.  It germinates early in the season, grows rapidly, and has a very effective seed dispersal system: when it dries, it breaks away from the ground at the base of the plant and tumbles along with the wind scattering its seeds.  It has all the traits necessary for easy and widespread dispersal and growth.

Sisymbrium altissimum commonly grows to three feet (as pictured here) and can reach nearly five feet.  It branches in a maze of stems, produces numerous flowers, and quickly goes to seed.  The dried plant is buff colored and very stiff.

Linnaeus named both this genus and species in 1753. "Sisymbrium" is a name given by the Greeks to some Mustard plant several thousand years ago.  "Altissimum" is Latin for "very tall".

Semi-desert, foothills. Disturbed areas. Spring, summer.
Hawkins Preserve, Cortez, Colorado, May 23, 2006.

Two-to-three inch long seed pods (on the right side of the photograph) grow very rapidly.

Semi-desert, foothills. Disturbed areas. Spring, summer.
Hawkins Preserve, Cortez, Colorado, May 23, 2006.

Lower leaves are deeply cut and saw-toothed; upper leaves are cut as deeply but are not saw-toothed.