Garlic mustard

Garlic mustard (Alliaria petiolata)

Herbaceous biennial with stems 2-4’ tall. First-year plants form a basal rosette that remains green through the winter. Second-year plants produce one to several flowering stems.

Overview

Regulated areas of garlic mustard
Garlic mustard is Restricted (Orange counties)

Other names for this plant include:

  • Common names: mustard root, garlic root, garlicwort
  • Scientific names: Alliaria officinalis; Alliaria alliaria; Arabis petiolata

Ecological threat:

  • Invades high quality upland and floodplain forests and savannas, as well as disturbed areas, such as yards and roadsides. It is sometimes found in full sun, though most often grows in areas with some shade, and does not do well in acidic soils.
  • Native herbaceous cover has been shown to decline at sites invaded by garlic mustard.
  • Garlic mustard exudes antifungal chemicals into the soil that disrupt associations between mycorrhizal fungi and native plants, suppressing native plant growth.

Classification in Wisconsin: Restricted

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for garlic mustard was based upon this literature review developed by the department.

Identification

Leaves: First year plants have basal leaves that are dark green, heart or kidney-shaped, with scalloped-edges and wrinkled appearance. On second year plants, stem leaves on flowering plants are alternate, triangular, with large teeth, and up to 2-3” across. Leaves and stems smell like garlic when crushed.

Flowers: Small, white, 4-petaled, and abundant. Bloom throughout the spring.

Fruits & seeds: Seed pods are long (1-2 ½)”, slender capsules (siliques) green in color, drying to pale brown. Inside, seeds are small, shiny black, and arranged in a single row. Plants can be recognized in late summer and fall by their dry, papery brown, erect seedpods atop dead stalks. Seeds remain viable in the soil for at least 7 years.

Roots: White, slender taproot, “S”-shaped at the top. Will resprout from the root crown if only the top of the plant is removed.

Similar species: Several native white flowered plants, the toothworts (Dentaria spp.) and sweet cicely (Osmorhiza claytonii), bloom at about the same time as garlic mustard and may be mistaken for it. The leaves of native violets (Viola spp.) and the non-native creeping Charlie (Glechoma hederaea) may be mistaken for first year garlic mustard plants, but they will not have a garlic odor when crushed.

Distribution

Known county distribution of garlic mustard
Counties in WI where garlic mustard has been reported (as of July 2011). Both vouchered and unvouchered reports included.

Do you have garlic mustard in your county but it isn't shaded on the map? Send us a report.

Control

Mechanical: Hand pull in early spring before seed set. If plants are flowering, place in plastic bags for trash disposal or burn. Cut plants at their base just after the flower stalks have elongated but before any flowers have opened; may have to cut more than once during a growing season. Place pulled/cut plants in plastic bags for trash disposal. Use controlled burns in fall or early spring.

Chemical: Foliar applications of glyphosate in early spring or late fall when native plants are dormant.

For more information on control techniques, visit the Garlic Mustard factsheet [exit DNR] by University of Wisconsin-Extension.

Photos

View garlic mustard pictures in our photo gallery!

Resources

Sources for content:

  • Czarapata, Elizabeth; Invasive Plants of the Upper Midwest: an illustrated guide to their identification and control. University of Wisconsin Press. 2005. Pg. 46-52
  • Fewless, Gary. Herbarium, Cofrin Center for Biodiversity, UW-Green Bay. Invasive Plants of Wisconsin. Alliaria petiolata [exit DNR].
  • Invasive Plants Association of Wisconsin. Major Concerns: Garlic Mustard [exit DNR].
  • Rowe, Pamela and Jil M. Swearingen. Plant Conservation Alliance, Alien Plant Working Group. Least Wanted: Garlic mustard [exit DNR]. Last updated June 2005.

Links for More Information

Last revised: Friday October 03 2014