Photographer: Joseph M. DiTomaso Affiliation: University of California - Davis Source: Bugwood.org Copyright: (CC BY-NC 3.0)
Saharan mustard (Brassica tournefortii) is an annual plant that prefers sandy soil, and is known to live in unfavorable environmental conditions where no other plants can grow. This rapid growing plant has almost leafless stems that grow about 2 feet from the plant creating a bush appearance. Small yellow flowers appear during the summer and fall months before producing seed pods. Mature plants can dry up and break off forming a tumbleweed that could be mistaken for the invasive Russian thistle.
Like many invasive plants, the Sahara mustard plant grows rapidly, and is known for out-competing native plants for vital resources. Wildflowers in the Lower Colorado River Valley are at high risk for complete eradication due to the Saharan mustard. Many other wildflower fields across California and Arizona are now 75% occupied by Saharan mustard preventing wildflowers and other native shrubs from growing. During dry months Sahara mustard becomes and extreme fire hazard capable of spreading fire across sand dunes. In areas where native plants can't tolerate fire, a barren landscape forms that later becomes dominated by various exotic weeds.
Sahara mustard is a self pollinating plant, capable of producing thousands of seed pods on every yellow flower that develops. Larger plants can produce up to 16,000 seeds that become sticky with a mucous film to facilitate transport via animal fur or vehicles. Dry plants are known to break off and tumble to disperse seeds in the same fashion as the invasive Russian thistle (Salsola tragus).
Sahara mustard was first discovered in the U.S. in 1927 near California's Coachella Valley where it was likely introduced as a seed contaminant. During the 1990's Sahara mustard slowed in spread due to severe drought. However, within the last ten years the plant has become widely established and adapted for a large variety of substrates. Spreading eastward across the southern United States, Sahara mustard became a large concern for botanists in 2005.
Native Origin: Sahara mustard is native to a large part of the Old World extending from North Africa to the Middle East to Southern Europe and Pakistan.
U.S. Habitat: Sahara mustard has become adapted to a large variety of habitats, and can be found in many areas throughout the southern U.S. Traditionally the desert plant preferred sandy soils and required little water to survive. Now Sahara mustard can grow along rocky hillsides, poor quality soils, deserts, and along crop fields.
U.S. Present: AZ, CA, NM, NV, TX
Management of Sahara mustard is in the early stages with preliminary surveys being conducted to asses the damage potential and location of the plant. In small areas of establishment Sahara mustard can be erradicated manually by pulling the entire plant from the ground prior to seed formation. All plants should be disposed of and not left on the ground where they were pulled. Herbicide can be effective prior to seed formation immediately following rain.
Felger, R.S. 1990. Non-native plants of Organ Pipe Cactus National Monument. Tech. Rep. 31. Tucson: Cooperative National Park Research Studies Unit.
Malusa, Jim, Bill Halvorson, & Deborah Angell. 2003. Distribution of the exotic mustard Brassica tournefortii in the Mohawk Dunes and Mountains, Arizona. Desert Plants 19(1):31-36.
Minnich, R.A. and A.C. Sanders. 2000. Brassica tournefortii Gouan. In: Bossard, C.C., J.M. Randall, and M.C. Hoshovsky. eds. Invasive Plants of California's Wildlands. University of California Press, Berkeley and Los Angeles. 360 pp.
Van Devender, T.R., R.S. Felger, and A. Burquez M. 1997. Exotic Plants in the Sonoran Desert region. 1997 Symposium Proceedings, California Exotic Pest Plant Council.