4. tumbleweed, commonly found in the western united states, is the dried structure of certain plants that are blown by the wind. kochia, a type of plant that turns into tumbleweed at the end of the summer, is a problem for farmers because it takes nutrients away from soil that would otherwise go to more beneficial plants. scientists are concerned that kochia plants are becoming resistant to the most commonly used herbicide, glyphosate. the us department of the interior claims that 20 percent of kochia plants are resistant to glyphosate. in 2017 another study by researchers at university of new mexico, 38.5 percent of 52 randomly selected kochia plants were resistant to glyphosate.