Answer: The rhizomes (underground runners) are so deep that digging or pulling at it only encourages it to grow. I have read that you can dig down 12-18" and find evidence of this noxious plant.
It will probably take repeated applications of a glyphosate based product like Roundup to frustrate Bishop's Weed and then kill it, but with time and persistence, it can be done. If it's growing into your lawn, you may have to sacrifice some turf in the short term.
If you think about the way glyphosate works, it makes sense to avoid products that contain the "quick kill" chemical. In order to kill the plant, the chemical needs to be transported through the foliage down into the roots. If the foliage is killed off too quickly, the chemical can't make it to the roots, and the topgrowth will die off, but the plant will survive.
Also, once the chemical dries on the foliage, it is no longer being transported through the plant tissue, so wet down the plant before spraying it. Don't spray when the wind speeds are more than 8-10 mph, to avoid drift and rapid drying on the foliage. Be patient, keep at it, and good luck!
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