One day last week, Jim stopped on the walkway up to our kitchen door and looked down at the green stuff growing in the sloping strip between our house and the woods. I say “green stuff” because it isn’t turfgrass, but a mixture of various weeds and white clover that Jim planted to help combat erosion and improve the soil, and (ouch), a border of mugwort that I unknowingly introduced with some herb cuttings I brought from another site several years ago.

I say “Ouch,” because mugwort is not a plant you want in your lawn or garden. Common mugwort (Artemisia vulgaris), like all 200 to 400 Artemisia species, is a member of the Aster (daisy) family of herbaceous perennials or woody shrubs. Many Artemisias are native to eastern and southern Europe, Eurasia, and northern and southern Africa and were introduced into North America. Others are western North America and Mexico natives.

Numerous species have found homes in American gardens, where their silver-gray foliage and aromatic fragra...