Hoary mugwort (Artemisia stelleriana or Artemisia ludoviciana) is a perennial plant known for its distinctive silvery-gray foliage. It belongs to the Asteraceae family, which includes sunflowers and daisies. While some varieties are cultivated for ornamental appeal, its vigorous growth habit can lead it to be considered a weed. This adaptable plant thrives across a range of conditions and is found globally, with native distributions in East Asia and North America.
Identifying Hoary Mugwort
Hoary mugwort’s foliage is typically covered in dense, soft, white or silvery hairs, giving it a “hoary” or felted appearance. These hairs contribute to its common name, “Dusty Miller,” and help the plant conserve water and reflect sunlight. Its leaves are deeply lobed or toothed, often described as feather-like, and range from 2 to 4 inches in length, arranged alternately along the stem.
It grows as an herbaceous perennial, forming spreading clumps 1 to 3 feet tall, sometimes reaching 4 feet. Its stems are often greenish-white and can have a slightly woody base. While primarily grown for its foliage, hoary mugwort produces tiny, inconspicuous yellow or creamy-white flowers in dense clusters or loose panicles at the stem tips, usually from mid-summer to early fall. These small, disk-shaped flowers are not particularly showy.
Its Impact and How It Spreads
Hoary mugwort is highly adaptable, commonly found in disturbed areas, along roadsides, in waste places, and in various garden settings. It prefers well-drained soils and full sun, but tolerates a range of conditions including drought, poor soils, and salt spray.
The primary method of spread for hoary mugwort is its extensive underground rhizome system, which allows it to form dense, spreading colonies. These rhizomes enable vegetative expansion, with new plants emerging from root fragments. While it also produces numerous seeds that can remain viable for several years, rhizome dispersal is generally the main driver of its aggressive spread.
This plant can outcompete native vegetation and desired garden plants, forming monocultures that reduce biodiversity. Additionally, its pollen is a known allergen, contributing to hay fever and asthma for some individuals.
Management and Control Strategies
Managing hoary mugwort requires a persistent, multi-pronged approach. Cultural practices can help prevent its establishment or reduce its vigor. Ensuring good soil drainage and avoiding overwatering creates less favorable conditions, as the plant prefers drier environments. Maintaining healthy, dense stands of desirable plants can also limit mugwort’s ability to colonize new areas by outcompeting it for resources.
Mechanical control methods can be attempted, though they present challenges. Hand-pulling is effective for small infestations, but it is important to remove as much of the rhizome system as possible, as fragments can easily resprout. Mowing can suppress growth and prevent seed production, but it is insufficient alone, as rhizomes can regenerate even after repeated mowing. Tilling is not recommended as it can fragment rhizomes and inadvertently spread the plant further.
Chemical control can be an option, but success depends heavily on the type and timing of application. Non-selective herbicides like glyphosate can be used for spot treatments where no other plants are desired. Selective herbicides, such as those containing clopyralid or triclopyr, may offer more targeted control in lawns or specific landscapes. Due to hoary mugwort’s dense, hairy foliage, a surfactant might be necessary to improve herbicide penetration. Applying herbicides in late summer or early fall, when the plant is actively translocating resources to its roots, can increase effectiveness. However, chemical control often requires repeat applications and may need integration with other methods to achieve lasting results.