Garlic mustard, Alliaria petiolata

Life Cycle

Annual, winter annual or biennial.

Propagation

Reproduces only by seed.

Stems

Stems up to 1m tall, simple or little branched, smooth or with a few simple hairs.

Leaves

Winter annual and biennial forms produce rosettes of leaves (A); these leaves varying from few to many, from kidney-shaped with a broad, rounded tip (a) to narrower and ovate with a rounded or nearly acute tip (b), their margins toothed with shallow, rounded to deep, coarse, pointed teeth; lower stem leaves alternate, broad and kidney-shaped, to 10cm wide and long, with coarsely toothed margins, becoming longer and narrower upward; upper leaves deltoid, 1-7cm long and wide, or somewhat rhombic, with acute tip and coarsely toothed margins.

Flowers and Fruit

Flowers small, white, with 4 petals 3-6mm long and wide, the lowermost 1-3 flowers and seedpods may be in the axils of small leaves; seedpods (siliques)(d,C) 0.4-5cm long, spreading, and borne on short pedicels about as thick as the pods; their beaks (f) slender, 1-3mm long; seeds black, 3mm. The whole plant has a distinctive onion-like or garlic-like odour. Flowers from May to June.

Habitat

Introduced and naturalized from Europe, Garlic mustard is now found in moist woods, swampy areas and ditches and along roadsides and railway embankments throughout southern Ontario. It occasionally invades adjacent cultivated land.

Competitiveness

Garlic mustard is the “purple loosetrike” of fencerows and woodlands – it is a threat to many natural species. It completes with native flora, invading to monopolize light, soil nutrients. It competes with native wildflowers that also flower in the spring, like spring beauty, wild ginger, bloodroot, Dutchman's breeches, hepatica, toothworts, and trilliums, stealing light, moisture, nutrients, soil and space. Wildlife and insects that depend on these early plants for food soon disappear. Cows that graze on this weed produce milk with a garlic flavour.

Distinguishing Features

It is distinguished by its broad leaves with rounded to coarse teeth, small white flowers and garlic-like odour. Mature plants are distinguished from Wild mustard by their seedpods being more slender and having a slender beak that is never broad or flattened, and never containing an additional seed or two, and in some plants of Garlic mustard the lowermost 1-3 flowers or seedpods may be in the axils of small leaves, a characteristic it shares only with Dog mustard.

Human Health Issues

The fruit, flowers and leaves of garlic mustard are edible as food for humans and are best when young. They have a mild flavour of both garlic and mustard which have been used in pesto and salads. Raw or cooked greens of young plants contain vitamins A, B, and C. Tilford, G.L. (1997) Edible and Medicinal Plants of the West. p.158. Mountain Press Publishing, Montana, USA.


Figure #1.

Garlic Mustard. A. Rosette. B. Plant just beginning to flower. C. Top of older plant with many seedpods.


Figure #10.

Roots of garlic mustard.


Figure #11.

Dried out garlic mustard seedhead.


Figure #12.

Seeds of garlic mustard


Figure #2.

Young garlic mustard plant.


Figure #3.

Flowers of Garlic mustard.


Figure #4.

Flowers of Garlic mustard.


Figure #5.

Seedpods of garlic mustard.


Figure #6.

Toothed leaf of garlic mustard.


Figure #7.

Alternate leaf arrangement of Garlic mustard.


Figure #8.

Garlic mustard at roadside in Central Ontario growing in late May/early June.


Figure #9.

Garlic mustard mature plant.