The following is information on control of mugwort in landscape beds.
Many landscape beds have problems with mugwort (Artemesia vulgaris), also know as wild chrysanthemum. This is a perennial weed that is difficult to control due to its ability to spread by underground rhizomes. Leaves are similar to appearance as chrysanthemum, 2-4 inches long, 1-3 inches wide, simple, alternate, deeply lobed, and are covered with soft, white to gray hairs underneath. Leaves will also have a distinctive smell. Mugwort is most commonly introduced as a weed with nursery stock. It rarely produces viable seed and spreads almost exclusively by rhizomes.
Hand weeding is often only partially effective because complete control requires removal of all the underground rhizomes. One fairly effective control approach is to use directed applications of glyphosate, one in late summer and one in early fall. Dichlobenil (Casoron) granular herbicide, winter applied, has given good mugwort control in beds with woody plants such as junipers; however, Casoron is not labeled for all species and injury can occur on newly planted trees and shrubs. Clopyralid (Lontrel) has given up to 95% control of mugwort in some trials as a selective application. However, clopyralid is only labeled for use around the following woody species: dogwood, oak, fir, pine, red maple, spruce, sycamore, arborvitae, boxwood, juniper, some Rhododendron species, spirea, and yew. A better fit for Lontrel is suppression of mugwort in ornamental grasses where it can be used as an over-the-top application for many grass species.
Gordon Johnson, Extension Horticulture Agent, UD, Kent County