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Sisymbrium altissimum
Sisymbrium altissimum
Sisymbrium altissimum (Jim Hill Mustard)
Brassicaceae (Mustard Family)

Semi-desert, foothills. Disturbed areas. Spring, summer.
Above: Near Yellow Jacket Canyon, May 27, 2015.
Left: Hawkins Preserve, Cortez, Colorado, May 23, 2006.

Sisymbrium altissimum is a native annual of Europe that 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 has a stout central stem, commonly grows to three feet (as pictured above) 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.

At left you can see the progress from buds at the far left, to just opening flower, to fully open flower, to developing seed pod at far right.  The four bright yellow petals of the top flower are subtended by four narrow, green/yellow sepals which are cupped at their tips.

Linnaeus named both this genus and species in 1753. "Sisymbrium" is a name given by the Greeks several thousand years ago to a plant in the Mustard Family.  "Altissimum" is Latin for "very tall".  Jim Hill was a railroad owner and this non-native species is thought to have spread across the United States along the railroad.

Sisymbrium altissimum
Sisymbrium altissimum (Jim Hill Mustard)
Brassicaceae (Mustard Family)

Semi-desert, foothills. Disturbed areas. Spring, summer.
Near Yellow Jacket Canyon, May 27, 2015.

Plants quickly elongate, flowering at the top, and producing larger and larger seed pods farther down the stem. The white arrows point to pods nearly five inches long.

Sisymbrium altissimum
Sisymbrium altissimum (Jim Hill Mustard)
Brassicaceae (Mustard Family)

Semi-desert, foothills. Disturbed areas. Spring, summer.
Near Yellow Jacket Canyon, May 27, 2015.

Lower leaves are deeply cut into broad leaflets and are saw-toothed; upper leaves are cut as deeply but the leaflets are very narrow (linear to filiform) and they are not saw-toothed.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Sisymbrium altissimum