Artemisia vulgaris, commonly known as Mugwort, is an aggressive perennial weed that challenges gardeners and landscapers. Native to Europe and Asia, this plant has established itself across North America, rapidly forming dense patches that displace other vegetation. Mugwort thrives in a wide range of soil conditions, making it a formidable opponent. Natural control is difficult due to its extensive, underground root system, which allows it to persist and regenerate after surface removal. Controlling this weed without chemical agents requires a multi-season commitment focused on exhausting the plant’s energy reserves.
Identifying Mugwort and Its Underground Network
Mugwort is easily recognized by its distinctive foliage, which is dark green and hairless on the upper surface. The undersides of the deeply lobed leaves are covered in dense, woolly, silver-white hairs, creating a striking two-toned appearance. When crushed, the leaves emit a strong, sage-like or spicy scent. The angular stems are often purplish-brown and can grow two to five feet high, becoming woody as they mature.
The plant’s persistence is due to its expansive network of rhizomes, which are horizontal underground stems. These rhizomes allow the plant to spread rapidly, creating large colonies in disturbed soils. The Mugwort rhizome system is shallow, extending mostly within the top 8 inches of the soil. Mugwort can regenerate an entirely new plant from rhizome fragments as small as 2 centimeters, meaning cutting the plant at the surface is ineffective. Control attempts must target this dense, regenerative network beneath the soil.
Physical Removal Methods: Digging and Smothering
For smaller, contained infestations, manual excavation is the most direct and thorough method of natural control. This method requires diligence and precision to ensure every fragment of the regenerative root system is removed. Begin by cutting the Mugwort stalks down to the ground to make the area accessible. Then, dig out the infested soil to a depth of at least 10 to 12 inches to capture the majority of the rhizome mass.
After excavation, the soil should be carefully sifted by hand to locate and remove all visible pieces of the brown, woody rhizomes. Missing small root fragments will allow the Mugwort to resprout, negating the intensive effort. The excavated soil and plant material must not be composted on-site, as the rhizomes may survive and spread. Instead, dispose of the material in a sealed container or bag where fragments cannot take root.
For larger areas where manual digging is impractical, the smothering technique starves the Mugwort of light and oxygen. This process involves layering thick materials over the entire infested area to block photosynthesis. A heavy layer of overlapping cardboard or several sheets of newspaper should be placed directly over the weed patch. The barrier edges must extend well beyond the visible Mugwort growth to capture the furthest-reaching rhizomes.
Cover the paper barrier with a deep layer of organic mulch, such as wood chips or shredded leaves, four to six inches deep. This mulch helps hold the cardboard in place and adds weight to suppress emerging shoots. Mugwort is resilient, so this barrier must remain in place for a minimum of one full growing season, and often two. Maintaining the integrity and thickness of the light-blocking layers is necessary to exhaust the deep energy reserves stored in the rhizome network.
Using Solarization for Extensive Infestations
Solarization offers a non-chemical option for large, open areas heavily infested with Mugwort. This process uses the sun’s intense heat to “cook” the top layer of soil, sterilizing it and killing the rhizomes and weed seeds. To begin, mow the Mugwort down to the ground and then thoroughly water the area to a depth of about 12 inches. Wetting the soil stimulates the Mugwort seeds and remaining rhizome fragments to begin germination or growth.
Once the area is wet, cover the entire surface with a sheet of clear plastic, preferably UV-stabilized polyethylene four to six millimeters thick. Clear plastic is used because it allows solar radiation to pass through and become trapped, creating a greenhouse effect that raises the soil temperature far higher than black plastic would. The edges of the plastic must be completely sealed by burying them in a trench or weighing them down with soil, bricks, or rocks to trap the heat and moisture.
The most effective time for solarization is during the hottest, sunniest months of the year, typically late spring through mid-summer. The high temperatures generated under the plastic disrupt the cellular structure of the plant tissues and kill the rhizomes. The plastic should remain undisturbed for four to eight weeks, depending on the ambient temperatures and sunlight intensity. Continuous exposure to high soil temperatures is necessary to ensure the death of the deeper, hardier Mugwort rhizomes.
Long-Term Site Rehabilitation and Monitoring
Achieving initial removal is only the first phase of control; long-term success relies on cultural and preventative maintenance. After physical removal or solarization is complete, the exposed soil is susceptible to re-infestation from missed rhizome fragments or new seeds. Improving soil health and establishing a dense cover of desirable plants is the next step in site rehabilitation.
Planting a competitive cover crop immediately after removal helps outcompete emerging Mugwort sprouts for light, water, and nutrients. Fast-growing turfgrasses or aggressive, dense native groundcovers are effective choices for stabilizing the soil and providing a living barrier. A healthy, thick stand of desirable plants will shade the soil, which suppresses the germination of Mugwort seeds.
Establishing a rigorous monitoring schedule is necessary for preventing significant re-establishment of the weed. Regularly inspect the treated area, particularly along the edges where Mugwort is most likely to creep back in. Any new sprout must be pulled immediately, ensuring the entirety of the small rhizome is removed before it can establish an extensive network. This vigilance must be maintained for several years, as small underground fragments can remain dormant before attempting to regrow.