Russian thistle is a large weedy plant that is more commonly known as tumbleweed. The weeds are common across the Southwest, particularly along roadsides and in construction areas. Russian thistle depends on disturbance of the air and soil to help it self-sow its seeds. Because each tumbleweed produces thousands of seeds, it is difficult to control its population. With vigilant care, Russian thistle can be eradicated.
Treat the area with a broad-spectrum pre-emergent herbicide in early spring. This works to kill the Russian thistle before it emerges from beneath the soil. Follow the directions on your package of herbicide to increase chances of success.
Mow the area in mid to late spring, with the lawn mower blades set at the lowest setting. No pre-emergent herbicide is 100 percent effective, and some Russian thistle seedlings may remain. It is essential that you mow the area to cut down existing Russian thistle weeds before they mature and set seed.
Spray the area with a broad-spectrum post-emergent herbicide. Post-emergent herbicides work to kill weeds that have already germinated. Again, follow the directions on your herbicide's package, to ensure you apply the chemicals properly.
Spray the area with both pre- and post-emergent herbicide (first one, then the other) in late spring and early summer. These two chemicals work together to kill ungerminated seeds, as well as Russian thistle seedlings.