(M.Bieb.) Cavara & Grande
Alliaria petiolata is a biennial 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 Pakistan and western China (Xinjiang).
In the first year of growth, plants form clumps of round shaped, slightly wrinkled leaves, that when crushed smell like garlic. The next year plants flower in spring, producing cross shaped white flowers in dense clusters. As the flowering stems bloom they elongate into a spike-like shape. When blooming is complete, plants produce upright fruits that release seeds in mid-summer. Plants are often found growing along the margins of hedges, giving rise to the old British folk name of Jack-by-the-hedge. Other common names include Garlic Mustard, 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.
All parts of the plant, including the roots, give off a strong odor. In 17th century Britain, it was recommended as a flavoring for salt fish. It can also be made into a sauce for eating with roast lamb or salad. Early European settlers brought the herb to the New World to use as a garlic type flavoring, and as a good source of vitamins A and C. Its traditional medicinal purposes include use as a diuretic. The herb was also planted as a form of erosion control.
The plant is classified as an invasive species in North America. Since being brought to the United States by settlers, it has naturalized and expanded its range to include most of the Northeast and Midwest, as well as southeastern Canada. It is one of the few invasive herbaceous species able to dominate the understory of North American forests and has thus reduced the biodiversity of many areas.
It is an herbaceous biennial plant growing from a deeply growing, thin, white taproot that is scented like horseradish. In the 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. Second year plants grow from 30–100 cm (12–39 in) tall and rarely to 130 cm (51 in). The leaves are stalked, triangular to heart-shaped, 10–15 cm (3.9–5.9 in) long (of which about half being the petiole) and 5–9 cm (2.0–3.5 in) broad, with a coarsely toothed margin. The flowers are produced in spring and summer in button-like clusters. Each small flower has four white petals 4–8 mm (0.2–0.3 in) long and 2–3 mm (0.08–0.12 in) broad, arranged in a cross shape. The fruit is an erect, slender, four-sided pod 4–5.5 cm (1.6–2.2 in) 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 where that genotype is suited to thrive.
Cultivation and uses
Garlic mustard is one of the oldest discovered spices to be used in cooking in Europe. Evidence of its use has been found from archeological remains found in the Baltic, dating back to 4100-3750 B.C.E.
The chopped leaves are used for flavoring in salads and sauces such as pesto, and sometimes the flowers and fruit are included as well. These are best when young, and provide a mild flavor of both garlic and mustard. The seeds are sometimes used to season food directly in France. Garlic mustard was once used medicinally as a disinfectant or diuretic, and was sometimes used to heal wounds.
Sixty nine insect herbivores and seven fungi are associated with garlic mustard in Europe. The most important groups of natural enemies associated with garlic mustard were weevils (particularly the genus Ceutorhynchus), leaf beetles, butterflies, and moths, including the larvae of some moth species such as the Garden Carpet moth.
The small white flowers have a rather unpleasant aroma which attracts midges and hoverflies, although the flowers usually pollinate themselves. In June the pale green caterpillar of the orange tip butterfly (Anthocharis cardamines) can be found feeding on the long green seed-pods from which it can hardly be distinguished.
In North America, the plant offers no known wildlife benefits and is toxic to larvae of certain rarer butterfly species (e.g. Pieris oleracea and Pieris virginiensis) that lay eggs on the plants, as it is related to native mustards but creates chemicals that they are not adapted to. Native species, including two stem-mining weevils, a stem-mining fly, a leaf-mining fly, a scale insect, two fungi, and aphids (taxonomic identification for all species is pending) were found attacking garlic mustard in North America. However, their attacks were of little consequence to plant performance or reproduction of garlic mustard.
As an invasive species
Garlic mustard was introduced to North America as a culinary herb in the 1860s and is an invasive species across much of that continent. It is toxic or unpalatable to many native herbivores, as well as to some native lepidoptera. Biological control is the most promising control method. There are no effective native predators in North America. Control may be possible using predatory weevils. Chemical control is possible but unlikely to eradicate the plant given the likelihood of continual reintroduction from areas where it survives. Of the 76 natural enemies garlic mustard has in its native range, several have been tested for use as potential biological control agents, but none had been approved for use by May 2017. The monophagous weevil C. scrobicollis was nominated for approval in 2012 but blocked by the USDA Technical Advisory Group, TAG, group. It had seemed likely that TAG would approve its introduction in 2004 but it was also blocked then. It was also petitioned to TAG for approval in 2008, 2011, 2014, and 2016.
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|Wikiversity has bloom time data for Alliaria petiolata on the Bloom Clock|
|Wikisource has the text of a 1911 Encyclopædia Britannica article about Alliaria petiolata.|
- Flora Europaea: Alliaria petiolata
- Flora of China: Alliaria petiolata
- Flora of Pakistan: Alliaria petiolata
- Plants for a Future: Alliaria petiolata
- U.S. NPS guide
- Species Profile- Garlic Mustard (Alliaria petiolata), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Garlic Mustard.
- Most Unwanted - Garlic Mustard (Alliaria petiolata), Ontario Invasive Plant Council. Biological information and resources for Garlic Mustard in Ontario.