By Pat Ludwig
Mugwort is a non-native invasive plant that can quickly form dense colonies, crowding out native vegetation and making it difficult for other plants to return. Understanding how mugwort spreads—and when to take action—can help landowners manage small infestations before they become more difficult to control.
Mugwort can grow to 2–5 feet in height and often forms large, dense patches. Its leaves are deeply lobed, coming to a point at the end, green on top, and covered with fine, white-to-gray hairs underneath. The leaves also have a distinctive, sage-like smell when crushed. Mugwort likes open areas in full sun or partial shade where native plants grew before being pushed out by these invaders. It can often be found growing in colonies along roadsides, as the underground rhizomes like to wrap around asphalt the fill.
Early detection is ideal, as these “weeds” are not easy to successfully pull; pulling can stimulate the rhizomes. The plants spread by both seed and rhizomes, which can grow up to three feet long. These plants will go to seed in late July or early August.
Timing is important when managing mugwort. I’ve found that cutting or mowing prior to July can increase this invasive plant. It’s recommended to cut mugwort in July or mow large areas before the plants go to seed.
An organic method is to cover large colonies of mugwort with 1½ feet of fresh wood chips. This improves the soil beneath while creating conditions that can make it possible to successfully pull the entire plant with the rhizomes intact. Other gardeners have found success managing small areas by pulling the plants and then covering them with cardboard and mulch.
If a homeowner chooses to use herbicide, it can be applied from late August through October. Refer to the Connecticut Invasive Plant Working Group (CIPWG) website or your local Extension office for guidance. Whenever using herbicides, one must follow the manufacturer’s safety precautions and application instructions.
Mugwort can be difficult to manage and may take persistence. Finding the right approach can involve some trial and error, but early detection and proper timing can make a significant difference.