Hi, I moved to a new home, and found there is bishop's weed everywhere, through the lawn and in the garden beds. From what I've read online, it's nearly impossible to eradicate, but I'm hoping you can offer some hope. I am trying solarizing in one esp bad section, but given it's everywhere, that seems futile. I'm also considering digging out the soil in a garden bed, though that too seems a temporary measure. They say you can't leave even a piece of rhizome. Does this include only the thicker root pieces, or the thin white "hairs" also? I'm not normally a user of chemicals, but if it would work and be safe "enough", I'd be willing to douse the place and start fresh. Is there anything that would work? Thanks!
This is an instance when a systemic herbicide is the best solution. Systemic herbicides are absorbed into the system of the plant, down to the roots, and kill the roots.
Glyphosate is the ingredient that works best. Glyphosate is a total vegetation killer. If you are applying it in a bed, use a shied of cardboard or plastic to keep the spray off desirable plants. Late summer-early fall is a good time to use a systemic, because plants are translocating nutrients into their roots for the winter, and will move the herbicide more efficiently into the roots then.
If bishops weed is throughout the lawn, or in large sections, kill the area now (it's the best time of year to renovate a lawn anyway). Here is how to renovate your lawn: http://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/lawn_pubs/HG102...