Description

Garlic mustard is a cool season biennial herb in the mustard family (BrassicaceaeBrassicaceae a family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family; most are herbaceous plants, while some are shrubs) with stalked, triangular to heart-shaped, coarsely toothed leaves that give off an odor of garlic when crushed. First-year plants appear as a rosette of green leaves close to the ground. Rosettes remain green through the winter and develop into mature flowering plants the following spring. Flowering plants of garlic mustard reach from 2.0 to 3.5 feet in height and produce button-like clusters of small white flowers, each with four petals in the shape of a cross. Beginning in May, seeds are produced in erect, slender pods and become shiny black when mature. By late June, when most garlic mustard plants have died, they can be recognized only by the erect stalks of dry, pale brown seed pods that remain, and may hold viable seed, through the summer.

Habitat

Garlic mustard frequently occurs in moist, shaded soil of river floodplains, forests, and roadsides, edges of woods and trails edges and forest openings. Disturbed areas are most susceptible to rapid invasion and dominance. Though invasive under a wide range of light and soil conditions, garlic mustard is associated with calcareous soils but can also be found in acidic soils.

History and Introduction

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.

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.

Threats

Garlic mustard is an aggressive invader of wooded areas that can outcompete native herbaceous species, depriving them of light, moisture, soil, and space. Their high shade tolerance allows this plant to invade high quality, mature woodlands, where it can form dense stands. These stands not only shade out native understory flora but also produce allelopathica biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms compounds that inhibit seed germination of other species.

Dispersal Methods

Garlic mustard is mechanically dispersed. Its seeds usually fall just beneath the plant, but it is dispersed longer distances by people when seeds get attached to boots and clothing.

Control

Mechanical

Hand removal of entire root system of plant is practical for light infestations. For larger infestations cut stems at ground level or within several inches of the ground, to prevent seed production

Chemical

Herbicide may be applied for very heavy infestations. Fire can be used but can encourage germination of stored seeds and promote growth of emerging garlic mustard seedlings.