Garlic Mustard - Alliaria petiolata
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Garlic mustard (Alliaria petiolata) is a flowering plant in the Mustard family, Brassicaceae. It is native to Europe, western and central Asia, and northwestern Africa, from Morocco, Iberia and the British Isles, north to northern Scandinavia, and east to northern India and western China (Xinjiang). It often occurs along the margins of hedgerows, giving rise to the old British folk name of Jack-by-the-hedge. Other common names include Garlic Root, Hedge Garlic, Sauce-alone, Jack-in-the-bush, Penny Hedge and Poor Man's Mustard. The genus name Alliaria, "resembling Allium", refers to the garlic-like odour of the crushed foliage.
It is an herbaceous biennial plant (sometimes an annual plant) growing to 30-100 cm (rarely to 130 cm) tall. The leaves are stalked, triangular to heart-shaped, 10-15 cm long (of which about half being the petiole) and 2-6 cm broad, with a coarsely toothed margin. In biennial specimens, first-year plants appear as a rosette of green leaves close to the ground; these rosettes remain green through the winter and develop into mature flowering plants the following spring. Others flower and complete their life-cycle in their first year. The flowers are produced in spring and summer in buttonlike clusters, each flower small, white, with four petals 4-8 mm long and 2-3 mm broad, in the shape of a cross. The fruit is an erect, slender, four-sided pod 2-7 cm long, called a silique, green maturing pale grey-brown, containing two rows of small shiny black seeds which are released when the pod splits open. A single plant can produce hundreds of seeds, which scatter as much as several meters from the parent plant. Depending upon conditions, garlic mustard flowers either self-fertilize or are cross-pollinated by a variety of insects. Self-fertilized seeds are genetically identical to the parent plant, enhancing its ability to colonize an area. Although water may transport the seeds, they do not float well and are not carried far by wind. Long distance dispersal is most likely aided by human activities and wildlife.
In Europe as many as 69 species of insects and 7 species of fungi utilize Garlic Mustard as a food plant, including the larvae of some Lepidoptera species such as the Garden Carpet moth.
Garlic mustard was introduced in North America as a culinary herb in the 1860s and is now considered an invasive species. The insects and fungi that feed on it in its native habitat are not present in North America, increasing its seed productivity and allowing it to out-compete native plants. In addition, a study published in 2006 concluded that Garlic Mustard harms mycorrhizal fungi that some North American plants, including native forest trees, require for proper growth. Additionally, because White-tailed Deer rarely eat Garlic Mustard, large deer populations may help to expand it by removing competing native plants and exposing the soil and seedbed through trampling. A complication in the eradication of Garlic Mustard is the long time span in which seeds may remain viable in the ground. Seeds have been observed to germinate up to 11 years after being planted in the ground.
Website, video, and graphics by Rob Nelson
For more information on this plant or management please contact US Army Corp of Engineers