Alliaria petiolata

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Garlic mustard
Alliaria petiolata marais-belloy-sur-somme 80 26042007 3.jpg
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Brassicales
Family: Brassicaceae
Genus: Alliaria
Species: A. petiolata
Binomial name
Alliaria petiolata

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,[1] and east to northern Pakistan and western China (Xinjiang).[citation needed]

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,[2] 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 odor of the crushed foliage.

All parts of the plant, including the roots, give off a strong odor.


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,[3] 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.[4]

Close-up of Garlic Mustard flowers
Fruits and seeds

69 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.[5] 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.[6]

Cultivation and uses[edit]

Garlic mustard is one of the oldest spices used in Europe. Phytoliths in pottery of the Ertebølle and Funnelneck-Beaker culture in Northeastern Germany and Denmark, dating to 4100–3750 B.C.E.[7] prove its use. 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.[6] 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.[8] The herb was also planted as a form of erosion control.[9]

Today, 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, taste of both garlic and mustard. The seeds are sometimes used to season food in France.[8] Garlic mustard was once used medicinally[10] as a disinfectant or diuretic, and was sometimes used to treat wounds.[8]


Garlic mustard was introduced to North America by European settlers in the 1800s for culinary and medicinal purposes,[11] and has since spread all over North America, apart from the far south of the US and some prairie states and Canadian provinces.[12] It is toxic or unpalatable to many native herbivores, as well as to some native lepidoptera.[13][14][15][16] 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.[5]

Of the many natural enemies it has in its native range, several have been tested for use as biological control agents. Five weevil species from the genus Ceutorhynchus and one flea beetle were selected as candidates for preliminary testing in the 1990s. Since that time, those studying the candidates have narrowed the list to two-three weevils. Despite the demonstrated effectiveness of C. scrobicollis and C. constrictus in field testing, the importation and release of biological control agents such as those has been repeatedly blocked by the USDA's TAG (Technical Advisory Group). In particular, C. scrobicollis, which is monophagous and has been specifically studied since 2002, continues to be blocked, despite researchers' many petitions for approval.[17][18] It is currently estimated that adequate control of garlic mustard can be achieved by the introduction of just two weevils, with C. scrobicollis being the most important of the two.[19] Not one of the roughly 76 species that control this plant in its native range has been approved for introduction as of 2018 and federal agencies continue to spend millions on other, less-effective and more problematic, forms of control, such as chemical herbicides.[20]

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.[21][22] 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.[5]

Biological control is the most promising control method.[23][24][25][24][26][27] There are no effective native predators in North America.[28] Adequate control is considered likely with the introduction of just two weevils, one of which only feeds upon garlic mustard (monophagous)[29][30][29][31][32][24] Chemical control is possible but unlikely to eradicate the plant given the likelihood of continual reintroduction from areas where it survives.[33][33][32][34] 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.[29] The monophagous weevil C. scrobicollis was nominated for approval in 2012 but blocked by the USDA Technical Advisory Group, TAG. It had seemed likely that TAG would approve its introduction in 2004 but it was also blocked then.[35] It was also petitioned to TAG for approval in 2008, 2011, 2014, and 2016.[36] Federal agencies continue to spend millions on less-effective forms of control, while the introduction of biological control agents of any kind continues to be blocked.[37] Lead researchers have said funding is unavailable for continued research demanded by the TAG group.[34]


  1. ^ "Flora Europaea". Royal Botanic Garden Edinburgh.
  2. ^ "BSBI List 2007". Botanical Society of Britain and Ireland. Archived from the original (xls) on 25 January 2015. Retrieved 2014-10-17.
  3. ^ "Invader of the Month – Garlic Mustard – Alliaria petiolata" (PDF). Retrieved 2009-05-21.
  4. ^ PCA Alien Plant Working Group – Garlic Mustard (Alliaria petiolata)
  5. ^ a b c Van Driesche, R. "Garlic Mustard". Retrieved 19 May 2015.
  6. ^ a b Reader's Digest Nature Lover's Library, Field Guide to the Wildflowers of Britain, Editor Michael W. Davison, Art Editor Neal V. Martin, The Reader's Digest Association Limited, 11 Westferry Circus, Canary Wharf, London E144HE, Reprint 2001, ISBN 0 276 42506 5
  7. ^ Saul, Hayley; Madella M; Fischer A; Glykou A; Hartz S; et al. (21 August 2013). "Phytoliths in Pottery Reveal the Use of Spice in European Prehistoric Cuisine". PLOS One. PLOS. 8 (8): e70583. Bibcode:2013PLoSO...870583S. doi:10.1371/journal.pone.0070583. ISSN 1932-6203. PMC 3749173. PMID 23990910. Retrieved 22 August 2013.
  8. ^ a b c Gualtiero Simonetti (1990). Stanley Schuler, ed. Simon & Schuster's Guide to Herbs and Spices. Simon & Schuster, Inc. ISBN 0-671-73489-X.
  9. ^ Kleinstein, Debby. "Introduced Species Summary Project Garlic Mustard (Alliaria petiolata)". Retrieved 19 May 2015.
  10. ^ "Plants For A Future: Database Search Results". Retrieved 2009-05-16.
  11. ^ "GARLIC MUSTARD MONITORING ALONG THE BRUCE TRAIL IN THE NOTTAWASAGA VALLEY WATERSHED" (PDF). Nottawasaga Valley Conservation Authority. Retrieved 3 May 2018.
  12. ^ "Alliaria petiolata". Ontario Wildflowers. Retrieved 3 May 2018.
  13. ^ Haribal, Meena; Renwick, J.Alan A (1998). "Isovitexin 6"-O-β-d-glucopyranoside: A feeding deterrent to Pieris napi oleracea from Alliaria petiolata". Phytochemistry. 47 (7): 1237. doi:10.1016/S0031-9422(97)00740-1.
  14. ^ Daxenbichler, ME; Spencer, GF; Carlson, DG; Rose, GB; Brinker, AM; Powell, RG (1991). "Glucosinolate composition of seeds from297 species of wild plants". Phytochemistry. 30 (8): 2623–2638. doi:10.1016/0031-9422(91)85112-d.
  15. ^ Cipollini, D (2002). "Variation in the expression of chemical defenses in Alliaria petiolata (Brassicaceae) in the field and common garden". American Journal of Botany. 89 (9): 1422–1430. doi:10.3732/ajb.89.9.1422.
  16. ^ Rodgers, Vikki L.; Benjamin E. Wolfe, Leland K. Werden1 and Adrien C. Finzi (2008). "The invasive species Alliaria petiolata (garlic mustard) increases soil nutrient availability in northern hardwood-conifer forests". Oecologia. 157 (3): 459–471. Bibcode:2008Oecol.157..459R. doi:10.1007/s00442-008-1089-8. PMID 18612654.
  17. ^ Landis, Doug. "Management Options". Integrated Pest Management. Michigan State University. Retrieved 10 September 2017.
  18. ^ Reardon, Richard. "FHTET Biological Control Program — Sponsored Projects" (PDF). FHTET Biological Control Program. USDA Forest Service. Retrieved 10 September 2017.
  19. ^ Becker, R., 2017. Implementing Biological Control of Garlic Mustard – Environment and Natural Resources Trust Fund 2017 RFP.
  20. ^ Thiele, R. "Invasive Garlic Mustard: Love It Or Leave It?". WOSU Public Media. Retrieved 17 April 2018.
  21. ^ Pest Management Invasive Plant Control – Garlic Mustard (Alliara petiolata) USDA NRCS Conservation Practice Job Sheet MN-797
  22. ^ Davis, S., 2015. Evaluating threats to the rare butterfly, Pieris virginiensis. Wright State University.!etd.send_file?accession=wright1431882480&disposition=inline
  23. ^ Eubanks, HM.D., Hoffmann, J.H., Lewis, E.E., Liu, J., Melnick, R., Michaud, J.P., Ode, P., Pell, J.K., 2017. Biological Control Journal. Elsevier.
  24. ^ a b c Becker, R., Gerber E., Hinz H., Katovich E., Panke B., Reardon R., Renz R., Van Riper L., 2013. Biology and Biological Control of Garlic Mustard. The Forest Technology Enterprise Team.
  25. ^ UF IFAS, 2017. Biological Control. University of Florida.
  26. ^ Driesche, F.V.; Blossey, B.; Hoodle, M.; Lyon, S.; Reardon, R., 2010. Biological Control of Invasive Plants in the Eastern United States. USDA Forest Service. Forest Health Technology Enterprise Team.
  27. ^ Davis, Adam. 2009. Munching on Garlic Mustard – A New Weevil in the Works. United States Department of Agriculture – AgResearch Magazine.
  28. ^ Blossy, B., Ode, P., Pell, J.K., 1999. Development of Biological Control for Garlic Mustard. Cornell University.
  29. ^ a b c Becker, R., 2017. Implementing Biological Control of Garlic Mustard – Environment and Natural Resources Trust Fund 2017 RFP.
  30. ^ Katovich, J., Gerber, E., Hinz H., Skinner, L., Ragsdale, D., Becker, R., 2007. The Garlic Mustard Biocontrol Story – Past, Present and Future.
  31. ^ Orion T., 2015. Beyond the War on Invasive Species – A Permaculture Approach to Ecosystem Restoration.
  32. ^ a b Reardon, R., 2012. Garlic Mustard Biological Control — Forest Health Technology Enterprise Team.
  33. ^ a b Panke B., Renz M., 2012. Management of invasive plants in Wisconsin: Garlic mustard. University of Wisconsin-Extension Team Horticulture.
  34. ^ a b Becker, R., Gerber E., Hinz H., Katovich E., Panke B., Reardon R., Renz R., Van Riper L., 2013. Biology and Biological Control of Garlic Mustard Manual. The Forest Technology Enterprise Team.
  35. ^ Landis, Doug. "Management Options". Integrated Pest Management. Michigan State University. Retrieved 10 September 2017.
  36. ^ Reardon, Richard. "FHTET Biological Control Program — Sponsored Projects" (PDF). FHTET Biological Control Program. USDA Forest Service. Retrieved 10 September 2017.
  37. ^ Thiele, R. "Invasive Garlic Mustard: Love It Or Leave It?". WOSU Public Media. Retrieved 17 April 2018.

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