COMMON NAME

Garlic mustard


FULL SCIENTIFIC NAME

Alliaria petiolata (Bieb.) Cavara and Grande


FAMILY NAME COMMON

Mustard family


FAMILY SCIENTIFIC NAME

Alliaria petiolata


IMAGES


View of plant

Late seedlings

Basal rosette

Early seedlings

Inflorescence

Understory incursion

Incursion

Fruit close-up

Incursion

NOMENCLATURE/SYNONYMS

Synonyms: Alliaria officinalis Andrz. ex Bieb.


DESCRIPTION

Botanical Glossary

Alliaria petiolata is an herbaceous biennial whose flowering form can reach 1 m (3.3 ft.) in height. The first year plants are a basal rosette of leaves that remain green throughout the winter. They develop into mature flowering plants the following spring. The lower, dark green leaves are reniform (kidney-shaped), while the stem leaves are alternate and deltoid. The basal leaf blades can be 6-10 cm (2.4-4 in.) long and wide, while the stem leaves are 3-8 cm (1.2-3.1 in.) long and wide, gradually decreasing in size as they go up the stem. The margins of the leaves are coarsely toothed. The leaves give off a strong garlic odor when crushed. The flowers of Alliaria petiolata are consistent with those of the mustard family. That is, there are four white petals arranged in a cross shape, and these are 5-6 mm (0.25 in.) in diameter. The flowers are arranged in terminal racemes. They appear in the early spring (April-May), and fruits are produced by May. The cylindrical, shiny, black seeds are 3 mm (0.1 in.) in size and are contained in pods called siliques. These siliques are 2.5-6 cm (1-2.4 in.) long and 2 mm (0.08 in.) wide and contain 10-20 seeds. By June the plants are dead, often with the fruits still attached. Page References Gleason & Cronquist 197, Holmgren 180, Magee & Ahles 558. See reference section below for full citations.


SIMILAR SPECIES

None.


REPRODUCTIVE/DISPERSAL MECHANISMS

Alliaria petiolata is mechanically dispersed. It is still not known exactly how the plant moves over long distances.


DISTRIBUTION

Alliaria petiolata is native to Europe, where it can be found from England to the Czech and Slovak Republics, Sweden, Germany and south to Italy. It has also been reported from Canada. In the United States it can be found from Maine to South Carolina, West to Minnesota, Iowa, Arkansas, Oklahoma, Utah, Washington and Oregon. It has been reported from all New England States.


HISTORY OF INTRODUCTION IN NEW ENGLAND

Alliaria petiolata was first collected in Long Island in 1868. In New England it was first collected in Chester, Connecticut in 1897. It is likely that settlers planted it in the United States for food and medicinal purposes. It was probably introduced into New England by planting as well, and then it dispersed across the landscape.


HABITATS IN NEW ENGLAND

Abandoned Field,Early Successional Forest,Edge,Floodplain Forest,Late Successional Forest,Planted Forest,Roadside,Vacant Lot,Wet Meadow,Yard or Garden

Alliaria petiolata is successful in many types of habitats. It prefers moist, shaded areas, but can grow well at roadsides, edges of woods, along trails and in forest openings. Because of its shade tolerance it is one of few invasives that can be present and dominate a forest understory.


THREATS

Alliaria petiolata can outcompete native herbaceous species, depriving them of light, moisture and space. It also negatively impacts mycorrhizal fungi that are important underground symbionts for northern hardwood species, allowing it to compete with these woody species. In some states this plant threatens native butterfly species by outcompeting their native host plants. When the butterflies lay their eggs on Alliaria petiolata the larvae do not seem to survive as well. The seeds of Alliaria petiolata usually fall just beneath the plant, but it is probably dispersed longer distances by people when seeds get attached to boots and clothing.


MANAGEMENT LINKS

Illinois Natural History Survey
General description and management guidelines

The Connecticut Invasive Plant Working Group Invasive Plant Management Guide
Comprehensive management information

Plant Conservation Alliance
Fact sheet with management information

University of Wisconsin Weed Science


DOCUMENTATION NEEDS

Documentation required: Photograph of habit, flowers, basal leaves.
Best time for documentation: Spring, early summer.


ADDITIONAL INFORMATION

Integrated Taxonomic Information System
Taxanomic information

PLANTS database
Distribution, general information and links

Plant Conservation Alliance
Fact sheet

National Invasive Species Information Center
General information and many links

Adirondack Park Invasive Plant Program
Identification, fact sheet, management and distribution information in the Adirondack Park


REFERENCES

Anderson, R.C., S.S. Dhillion and T.M. Kelley. 1996. Aspects of the ecology of an invasive plant, garlic mustard (Alliaria petiolata), in central Illinois. Restoration Ecology 4(2): 181-191.

Anderson, Roger C. and Timothy M. Kelly. 1995. Growth of garlic mustard (Alliaria petiolata) in native soils of different acidity. Transactions of the Illinois State Academy of Science Volume 88, 3 and 4, pg. 91-96.

Blossey, Bernd, Victoria Nuzzo, Hariet Hinz, Esther Gerber. 2001. Developing biological control of Alliaria petiolata (M. Bieb.) Cavara and Grande (garlic mustard). Natural Areas Journal 21(4): 357-367.

Byers, D.L., J.A. Quinn. 1998. Demographic variation in Alliaria petiolata (Brassicaceae) in four contrasting habitats. Journal of the Torrey Botanical Society 125(2): 138-149.

Cruden, R.W., A.M. McClain and G.P. Shrivastava. 1996. Pollination biology and breeding system of Alliaria petiolata (Brassicaceae). Bulletin of the Torrey Botanical Club 123 (4): 273-280.

Fernald, M.L.  1950.  Gray's Manual of Botany 8th edition.  American Book Company, New York.

Gleason, H.A. and A.C. Cronquist.  1991.  Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed.  New York Botanical Garden, Bronx, New York.

Holmgren, N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual.  New York Botanical Garden, Bronx, New York.

Magee, D.W and H.E. Ahles. 1999.  Flora of the Northeast. University of Massachusetts Press, Amherst.

Meekins, J. Forrest, Harvey E. Ballard, and Brian C. McCarthy 1998. Morphological and genetic variation within and among populations of the non-indigenous invasive herb Alliaria petiolata (garlic mustard, Brassicaceae). American Journal of Botany 85 (6): 37.

Meekins, J.F. and B.C. McCarthy. 1999. Competitive ability of Alliaria petiolata (garlic mustard, brassicaceae), an invasive, nonindigenous forest herb. International Journal of Plant Sciences 160 (4): 743-752.


Meekins, J.F., H.E. Ballard and B.C. McCarthy. 2001. Genetic variation and molecular biogeography of a North American invasive plant species (Alliaria petiolata, Brassicaceae). International Journal of Plant Sciences 162 (1): 161-169.

Nuzzo, V.A. 1994. Response of garlic mustard (Alliaria petiolata Bieb - [Cavara And Grande]) to summer herbicide treatment. Natural Areas Journal 14 (4): 309-310.

Nuzzo, Victoria. 1993. Distribution and spread of the invasive biennial Alliaria petiolata (garlic mustard) in North America. Biological pollution: The control and impact of invasive exotic species 137-145.

Roberts, K.J. and R.C. Anderson. 2001. Effect of garlic mustard [Alliaria petiolata (Beib. Cavara & Grande)] extracts on plants and arbuscular mycorrhizal (AM) fungi. American Midland Naturalist 146 (1): 146-152.

Stinson, K.A., S.A. Campbell, J.R. Powell, B.E. Wolfe, R.M. Callaway, G.C. Thelen, S.G. Hallett, D. Prati and J.N. Klironomos. 2006.  Invasive plant suppresses the growth of native tree seedlings by disrupting belowground mutualisms.  PLOS Biology 4(5): e140.

Vaughn, S.F. and M.A. Berhow. 1999. Allelochemicals isolated from tissues of the invasive weed garlic mustard (Alliaria petiolata). Journal of Chemical Ecology 25 (11): 2495-2504.