Russian thistle or tumbleweed is a large bush with red or purple striped stems and sharp, spine-tipped leaves. This is particularly problematic for several reasons. It uses up a high level of nitrogen in the soil and will rob any neighboring plants of this essential nutrient. But what really makes Russian thistle a nuisance is its ability to spread rapidly. When these weeds mature, they are easily uprooted and blown around by the wind. And once wind-borne, each Russian thistle can deposit upwards of 200,000 seeds. Because it is so prolific, this plant must be carefully managed or it will quickly spread.
Physically remove Russian thistle. Since this plant is an annual, simply severing the above-ground vegetation from its roots with a sharp edged shovel will kill individual Russian thistle plants. The most effective time to do this is before July when the Russian thistle begins to flower and produce seed. If this is the only management method you apply, it will have to be repeated for several seasons before the Russian thistle stops coming back.
Spray Russian thistle with a combination of pre-emergent and post-emergent herbicides. Some gardeners prefer to circumvent the arduous task of manual digging with herbicides. However, these chemicals are rarely necessary in yards and gardens and may only have limited success. Post-emergent herbicide prescribed for use on Russian thistle like Roundup (glyphosate) or Vanquish (dicamba) are effective only when sprayed on immature Russian thistle that has yet to flower or harden. Pre-emergent herbicides like Aatrex (agrazine) or Devrinol (napropamide) are applied topically to the soil in problematic areas and incorporated into the soil via irrigation or rainfall. When choosing an herbicide, make sure that it is listed as safe to use on any desirable plants in the treatment area. Follow the manufacturer's instructions for application rates and methods.
Plant the formerly infested area with grass or another variety of thick-growing ground cover. Russian thistle cannot establish itself in areas with regularly irrigated and fertilized soil. When choosing a ground cover, be sure to choose a species that grows well in your area. The ground cover should be maintained for a minimum of two years to ensure that Russian thistle does not reemerge. After that, slower-growing plants can be planted.
Hand-weed any Russian thistle that reemerges or treat it with an herbicide listed as safe to use around the grass or ground cover that you have planted.