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Scientific Name:

Common Name:

Alliaria petiolata (Bieb.) Cavara & Grande
Garlic mustard
Family: Brassicaceae

USDA Plant Code: ALPE4

Habitat: Terrestrial; forest, waste areas

Growth Habit: Annual, Biennial Forb/herb

Native Environment: Europe

Introduction


Problems Caused
Garlic mustard [Alliaria petiolata (Bieb.) Cavara & Grande] is a cool-season biennial herb native to Europe. Other common names include jack-by-the-hedge and hedge garlic. It was introduced in the 1800s and escaped as early as 1868. Garlic mustard was once used in flavoring since it is high in Vitamins A and C. It is a serious pest in the northern United States, especially in woodlands where it may dominate the understory crowding out native vegetation.

Regulations
Garlic mustard is a Class A Noxious Weed in Alabama and Washington. In addition, garlic mustard seed are regulated under plant quarantine as Noxious in Washington. It is Banned in Connecticut and Prohibited in Massachusetts, Minnesota, and New Hampshire. Garlic mustard is a Quarantine and B designated weed in Oregon. It is a Class B Noxious weed in Vermont.

Description



Garlic Mustard Infestation in New England (Les Mehrhoff, IPANE)(Bugwood.org)
Vegetative Growth
Garlic mustard is a cool-season biennial from a taproot. It is often found in small to large colonies. Typically basal rosettes are produced the first year followed by one or more 2 to 4 foot flower stalks in the spring. Plants die after seed production, but remain standing and dispersing seed through the summer. Plants generally have a strong garlic odor when crushed.

Stems are erect and slightly ridged, with or without hairs. Leaves are alternately arranged on the stem. The early basal leaves tend to be kidney shaped, but later major leaves are heart-shaped to triangular, 1 to 3.6 inches long and wide. Leaf margins are shallow to coarsely wavy toothed. Leaf tips are often elongated. Petioles are 0.4 to 3 inches on stems, but reduced upward.

Flowering
Flowers are clustered at the stem apex, white with four petals. They appear from May to June. Fruit are 4-sided, erect to ascending, thin pods from 1 to 5 inches long and 0.06 inches wide. Fruiting plants gradually tan in color. As they mature, the pods may explode expelling numerous tiny black seeds up to 10 feet from the parent plant. Seed release can occur throughout the summer.

Dispersal
Garlic mustard is generally dispersed by seed drop, which may occur throughout the season. It may also be dispersed in contaminated soil or on contaminated equipment.


Garlic mustard in a Typical Woodland Setting Showing Leaves and Stems (Dan Tenaglia - missouriplants.com; © Karen Tenaglia)
Spread By
Mature seedbearing plants falling to the ground and people through movement of soil and contaminated equipment.

Habitat


Garlic mustard is a problem in pastures, fence rows, prairies, forest, roadsides, disturbed areas, and open woodlands. Garlic mustard exhibits shade tolerance and can form dense stands in woodland understory suppressing other vegetation through competition and allelopathy.

Distribution


United States
Garlic mustard is widespread in the northern United States, but apparently not escaped in the deep South. It occurs from Washington to Maine south to Oregon and northern Georgia. In the right habitat it can be quite common in certain northeastern states.

MidSouth
In the MidSouth, it has apparently not escaped in Alabama, Louisiana, and Mississippi. However, it has escaped in Arkansas and Tennessee. It seems to prefer cooler climates, but may be gradually moving south.

IPAMS Surveys:

Control Methods


Biological
Currently no know widespread biological controls are used in the United States for garlic mustard. Research with beetles for biocontrol is being conducted.

Chemical Control Options for Garlic Mustard
Common Name Trade Name Low Volume Rate/A
glyphosate Accord 1-2% v/v
Accord XRT II 1-2% v/v
metsulfuron methyl Escort XP 0.5 to 1 oz
Chemical
Larger infestations are generally best controlled by spraying with a herbicide. According to Renz (2008) and the Wisconsin Department of Natural Resources (2009) glyphosate can be used to control garlic mustard at 0.75 lbs ae/A or 1-2% ai, respectively. Renz (2008) also observed control on adult plants using Plateau at 6 fl oz product/A, Journey at 16 fl oz product/A, Banvel at 4 fl oz product/A, Oust at 0.5 oz product/A, Escort at 0.5 oz product/A, Sureguard at 3 oz product/A, Certainty at 2 oz product/A and Basagran at 16 fl oz product/A. However, some of these products do not list garlic mustard on the label and are not listed in the control table. If you have questions about these products, contact the manufacturer or your supplier. Because garlic mustard may develop a seed bank, multi-year applications may be necessary.

Mechanical
Mechanical controls can be successful for small infestations of garlic mustard. Small infestations may be removed by hand, although this method can be slow and labor intensive. Multiple approaches may be more feasible for larger populations. Removing plants prior to fruit ripening to avoid seed dispersal is suggested. Since seed may exist in the soil seed bank two to six years after plants have been removed, follow-ups are suggested.

Physical
Since garlic mustard grows in a wide range of conditions, physical control methods are generally not utilized.

References


Dupont. 2009. Website accessed on 30 July 2009. http://www2.dupont.com/Land_Management/en_US/assets/downloads/pdfs/IWM/K-14959.pdf

Mabberley, D.J. 1997. The plant-book: A portable dictionary of the vascular plants. 2nd ed. Cambridge University Press, NY.

Miller, James H. 2003. Nonnative invasive plants of southern forests: A field guide for identification and control. Southern Research Station, Asheville, NC.

Renz, M.J. 2008. Midwest Invasive Plant Network Conference. 2009. (Website accessed on 30 July 2009). http://mipn.org/2008%20MIPN%20conference/Thurs%20Session%20A%20AM/renz%20garlic%20mustard%20MIPN%202008%20compressed.pdf

USDA, NRCS. 2007. The PLANTS Database (http://plants.usda.gov, 6 August 2007). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Wisconsin Department of Natural Resources. 2009. (Website accessed on 30 July 2009). http://www.ipaw.org/invaders/garlic_mustard/GarlicMustardHandout.pdf

More Information


The Genus Alliaria belongs to the Mustard (Brassicaceae or Cruciferae) Family. Alliaria is not native to the MidSouth or United States. There are only two species of Alliaria, the second species occurs in Temperate Asia.

Contributing Authors


Dr. John D. Byrd, Jr., Plant and Soil Sciences, Mississippi State University
Dr. Randy Westbrooks, USGS, Biological Resources Discipline, Whiteville, NC.


Contact Info


Dr. Victor Maddox
Mississippi State University
Geosystems Research Institute
Box 9555
Mississippi State, MS 39762-9555
Ph. (662)325-2313
vmaddox@gri.msstate.edu

Geosystems Research Institute
Contact: John D. Madsen, Ph.D.  •  WebMaster