Alliaria petiolata - Garlic Mustard

Family: Brassicaceae (Mustard) [E-flora]

garlic mustard Alliaria petiolata

"Alliaria petiolata is a BIENNIAL growing to 1 m (3ft 3in) by 0.4 m (1ft 4in). It is not frost tender. It is in flower from Apr to June, and the seeds ripen from Jun to August. The flowers are hermaphrodite (have both male and female organs) and are pollinated by Bees, flies, lepidoptera, self.The plant is self-fertile.
It is noted for attracting wildlife.
Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: acid, neutral and basic (alkaline) soils. It can grow in full shade (deep woodland) or semi-shade (light woodland). It prefers moist or wet soil." [PFAF]

Introduction: "Garlic mustard is a highly invasive introduced species in the mustard family (Brassicaceae) that originates from Eurasia. In North America, it is found in many US states, particularly in the eastern US, though it is absent in the southern US states from Florida to California (USDA 2011). In Canada, it is found in British Columbia, New Brunswick, Nova Scotia, Ontario and Quebec. In Ontario, it is often a dominant understorey herb in disturbed sites and can form a thick ground cover. In BC, it is reported from the Okanagan, the Lower Mainland and the Victoria area. It is a biennial tap-rooted species with an erect form and white mustard-type flowers. It is easily recognized by its dark green kidney-shaped leaves and the noticeable garlic odour of crushed leaves. It is known to inhibit ectomycorrhizal fungi where it grows, which may influence seedling establishment of native species (Wolfe et al. 2008). There is evidence that some populations of this species in North America originated from the British Isles, though it is possible that there have been multiple introductions from other locations (Meekins et al. 2001)." [E-flora]

General: "Biennial herb from a taproot; stem erect and unbranched below inflorescence, sparsely hairy below, glabrous or with whitish bloom above, 20-120 cm tall; garlic smell, especially from root but also from crushed leaves." [IFBC-E-flora]

Notes: "Alliaria petiolata is considered an emerging invasive species in the Vancouver region by the Greater Vancouver Invasive Plant Council (2009). An emerging invasive is defined by them as: currently found in isolated, sparse populations but are rapidly expanding their range within the region." [E-flora]

Habitat / Range
"Mesic to dry disturbed sites and waste places in the lowland and lower montane zones; rare in SW and SC BC; introduced from Eurasia."[IFBC-E-flora]

Origin Status: Exotic. [E-flora]

Hazards

"a toxic FA, is sometimes reported in Cruciferae, for example, in Alliaria petiolata (Guil et al. 1997), and is also found in smaller amounts in some Caryopllyllaceae species, such as in Silene vulgaris (Alarcón et al. 2006). This FA, together with eicosenoic (20:1n-9) and nervonic (24:1n-9) acids, has been cited as responsible for congestive heart failure; so their presence in the diet has been associated with cardiotoxicity in humans (Imamura et al. 2013). In any case, the low fat content of the leaves makes it unlikely that the occasional consumption of A. petiolata (31 % EA of total FAs) would cause heart problems. However, it seems reasonable to avoid regular consumption of leaves or seeds of this species." [Tardio MWEP]

Food Usage

"Many species consumed during famine or food scarcity in the 19th century and during World War I in Germany and Austria [1], and common in Poland, e.g. Aegopodium podagraria and Alliaria petiolata, also do not appear in Polish culinary ethnographic literature either. The use of some of these species might have become obsolete before ethnographic studies began" [Luczaj,2007]

Other Usage

Herbal Usage

"Garlic mustard has been little used in herbal medicine[268]." [PFAF] "As its vernacular names indicate, Alliaria petiolata functioned as an alternative to garlic.Though that was chiefly in cooking, its leaves also substituted for garlic’s medicinally by being applied externally to sore throats in Kent (?)117 and chewed for sore gums and mouth ulcers in Norfolk.118 Rubbing the leaves on the feet was a cure for cramp in Somerset.119 More surprising, though, has been its use for wounds (again in Kent?).120" [MPFT]

Phytochemicals

[Doorduin&Vrieling,2011]

"Alliaria petiolata (garlic-mustard) has 19,000 units [of pro-vitamin A (beta carotene)] in its basal leaves" [Haines AP] "A. petiolata has the highest total carotenoid content (13.3 mg/100 g)" [Tardio MWEP]

"Despite sharing a common biosynthetic origin, the pathways of glucosinolates and cyanogenic glycosides are mutually exclusive [ 111 ] and coexist in only a few species in the order Brassicales (e.g., papaya ( Carica papaya ) and garlic mustard ( Alliaria petiolata )) and the Drypetes genus [ 119 , 124 , 125 ]." [Jetter FSAP]

Aerial Part
"Mustard oil
Content, %: 0.03–0.09 [1, 2]"
Seed
"Mustard oil
Content, %: 0.51–0.96 [1]
Oil, % on dry wt: 22–30 [3–5]" [LLCEOPS]

Leaves: 2.1% Fat (Dry wt.) [Tardio MWEP]

"The Eurasian invasive plant Alliaria petiolata has been shown to slow the rate of arbuscular mycorrhizal infection of native tree seedlings in North America. This leads to reduced tree seedling growth rates, thereby facilitating its invasion of relatively undisturbed forest habitats (Stinson et al., 2006). The allelochemicals produced by A. petiolata degrade mycorrhizal fungi and persist in the soil, preventing mycorrhizal recolonisation even when mycorrhizal fungi are added to it (Stinson, Klironomos & Acland, 2005). This change favours early successional species over late successional woody species and may alter the successional dynamics of the invaded woodland (Stinson, Klironomos & Acland, 2005). Naphthoquinones are known to have anti-fungal properties (Curreli et al., 2001) and may work in a way analogous to the isothiocyanates believed to be responsible for A. petiolata’s inhibitory effects." [Smith,2013]

"Stinson et al. (2006) presented novel evidence that antifungal phytochemistry of the invasive plant, Alliaria petiolata, a European invader of North American forests, suppresses native plant growth by disrupting mutualistic associations between native canopy tree seedlings and belowground AM." [Shah MNDCW]

"Prati and Bosdorf (2004) reported that Alliaria peteolata, a devastating invader of North American temperate forests also had stronger chemical effects on Geum laciniatum, a new North American neighbor, than on G. urbanum, its natural European neighbor." [Cheema Alleleopathy]

"Alliaria petiolata , another non-mycorrhizal exotic invader, not only reduces AMF in this way, it also produces allelochemicals which inhibit AMF spore germination, further disrupting natives’ mutualistic relationships (Roberts and Anderson 2001 ; Stinson et al . 2006 )." [Dighton IIS]

"Garlic mustard [Alliaria petiolata (Bieb) Cavara & Grande (Brassicaceae)] is an herbaceous biennial that has invaded, and now dominates, much of the hardwood forest understory in the eastern and midwestern United States and southeastern Canada (Cavers et al., 1979; Nuzzo, 1991, 1993, 1998). It is displacing native flora, and it is unlikely that its elimination from heavily infested areas is possible (Anderson et al., 1996). Populations of native understory plants have been found to decline in areas with a heavy infestation of garlic mustard, which can be as high as 20,000 seedlings/m2 (Trimbur, 1973; Yost et al., 1991). Groundcover by native ephemerals declined as cover by garlic mustard increased (Nuzzo, 1998). Recent studies have shown that garlic mustard may also pose a threat to organisms other than higher plants, as Porter (1994) reported that adults of the endangered West Virginia white butterfly [Pieris virginiana (W. H. Edwards)], which normally feed on several Dentaria spp. (Brassicaceae), preferentially laid their eggs on garlic mustard plants. This occurs even though the plant appears to be moderately toxic to the developing larvae (Haribal and Renwick, 1998)." [vaughn1999]

"The host plants of the native American butterfly Pieris napi oleracea include most wild mustards. However, garlic mustard, Alliaria petiolata, a highly invasive weed that was introduced from Europe, appears to be protected from this insect. Although adults will oviposit on the plant, most larvae of P. n. oleracea do not survive on garlic mustard. By using feeding bioassays with different larval stages of the insect to monitor the isolation and identification of two bioactive constituents that could explain the natural resistance of this plant, Renwick et al. (2001) found that a cyanopropenyl glycoside, alliarinoside, strongly inhibits feeding by first instars through an apparent post-ingestive feedback mechanism, while a flavone glycoside, isovitexin-6″- d-β-glucopyranoside, acts as a direct feeding deterrent that is perceived by taste receptors on the mouthparts of late instars. Interestingly, the first instars are insensitive to isovitexin-6"-D-B-glucopyranoside, and the late instars are little affected by alliarinoside." [Lattanzio RAPR]

Cultivation
"Prefers a damp rich alluvial soil[7, 53]. Succeeds in damp shady places where few other herbs will grow[238]. A good woodland edge plant, it also grows well in the bottom of hedgerows[24] and will self-sow freely in suitable conditions[238]. On a calm day the plant emits a strong smell of garlic. This is especially pronounced if the leaves are bruised[245]. This species is an important food source for the orange-tip butterfly[238]." [PFAF]

Deer Resistant: "Rawinski (2008) reported that deer eat many herbaceous species on the forest floor but avoid others.... They seem to disproportionately avoid exotic invasives such as ... garlic mustard (Alliaria petiolata). The end result is forest floors dominated by a few unpalatable native species and invasive exotics." [Beck PELD]

Propagation
"Seed - sow outdoors in situ either in spring or autumn." [PFAF]

Synonyms

References

Journals of Interest

Alliaria Sp.

The genus Alliaria contains 3 accepted, 17 synonyms and 1 unassessed species. [ThePlantList] There appears to be little information online about this genus. [PersonalNote]

Local Species;

References