Dear Fred

Thank you for reaching out to Ask Extension about the Mugwort on your property. This is an invasive plant that spreads by both seed and rhizomes. 

There are several ways to control this plant. Pulling in early spring as they first emerge, pulling out all roots. Mowing thru summer into the first weeks of September before seeds mature and are dispersed also helps control. Mowing after seeds mature will only disburse them.  Never till the soil around the mugwort as any remaining rhizomes will just start to grow again. If you can get a lot of them out and treat the soil, putting down cardboard or black fabric covered with heavy mulch will also assist in killing the remaining roots.

You are correct to use glyphosate to kill the plant but the better choices are triclopyr or clopyralid which work better for long term control. I have attached several links for articles to read. You may need to have someone  licensed in pesticide control to get rid of this invasive plant. It may take more than a year to completely remove all of the invasive plant.

UCONN - Mugwort
UMD - Mugwort

WVU - Mugwort