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GARLIC MUSTARD
Alliaria petiolata

Other Names | Origin & Distribution | Plant Description | Similar Species | Biology | Toxicity | Facts & Folklore

Garlic mustard flowering stalk. Young garlic mustard rosette. Garlic mustard flowering stem and leaf. Garlic mustard seeds. Garlic mustard rosette. Dried seedpods of garlic mustard. Garlic mustard rosette, showing typical leaf shape. Garlic mustard flower. Garlic mustard habit in woods. Thick stand of garlic mustard plants in flower.

Family: Mustard Family (Brassicaceae)

Other Names: Alliaria alliaria, Alliaria officinalis, Erysimum alliaria, Sisymbrium alliaria, Sisymbrium officinalis, garlic root, garlicwort, hedge garlic, Jack-by-the-hedge, poorman's-mustard, sauce-alone.

Origin and Distribution: Garlic mustard was brought to North America from Europe, most likely as a medicinal herb or green vegetable. It was first described in the U.S. on Long Island, New York in 1868. Since then, populations of garlic mustard have been reported in 30 states, mostly in the Northeast and Midwest. Garlic mustard is distributed throughout Ohio in moist woods and swampy areas and along forest edges and stream banks. It also invades disturbed areas such as roadsides and railways and is becoming a troublesome weed in reduced tillage. This species is usually found in shaded conditions, but is becoming more and more common in full sun. It prefers to grow in moist, rich soil, but can tolerate drier sites.

 

Plant Description: Garlic mustard is a biennial that forms a rosette the first spring and an upright stem with small white flowers the second spring. It is characterized by triangular, coarsely toothed leaves and a slender taproot with a distinct S-curve just below the root crown. Young leaves give off a strong garlic odor when crushed, but the odor fades with leaf age and is nearly gone by fall. Garlic mustard reproduces only by seeds.

  • Root system - Garlic mustard has a slender, white taproot that curves into a distinctive S-shape just below the crown.
  • Seedlings & Shoots - Young plants form rosettes of dark green, kidney-shaped leaves that have scalloped edges and long hairy leaf stalks (petioles).
  • Stems - Stems are usually smooth (sometimes with sparse hairs) and unbranched. They can grow from 1/2 to 3 1/2 feet tall. One plant usually produces 1 to 2 stems (sometimes more).
  • Leaves - Rosette leaves are dark green, kidney- to heart- to egg-shaped, shallowly toothed, and 2 to 4 inches in diameter. Stem leaves are alternate (1 per node), coarsely toothed, and triangular to heart-shaped. Stem leaves are largest (2 to 4 inches wide and long) on the lower portion of the stem, and become smaller toward the top of the stem. Both rosette and stem leaves have long, hairy leaf stalks (petioles) (1/2 to 2 inches long).
  • Flowers - Flowers are borne in clusters at the tops of stems. Each flower consists of 4 white petals that are about 1/4 inch long and form the shape of a cross.
  • Fruits & Seeds - The fruit is a long, narrow pod (1 to 2 inches long). Each pod contains an average of 16 small, black, oblong seeds (1/4 inch long, 1/8 inch in diameter).
 
Similar Species: The rosettes of other species including violets (Viola spp.) and white avens (Geum canadense) may be confused with young rosettes of garlic mustard, but only garlic mustard gives off a strong garlic odor when crushed. The flowering stage of garlic mustard may be confused with dame's rocket (Hesperis matronalis), also a spring blooming mustard that forms upright flowering stems and white flowers (sometimes pink). However, the flowers of dame's rocket are much larger and showier than those of garlic mustard, its leaves are lance-shaped and crushed foliage does have a garlic odor.
 

Biology: Seeds of garlic mustard germinate from late February to mid-May, and form leafy rosettes that persist through the summer and winter. Surviving rosettes produce erect flowering stems the following March, and flowers appear from April to May. Seeds begin to ripen in mid-June and are shed continually through September. Only a few seeds germinate the first spring. Most seeds germinate the second spring after their production. Remaining seeds can stay viable in the seedbank for 5 to 6 years. The number of seed pods produced per plant varies greatly. The smallest plants may produce only 1 or 2 pods, while large plants can produce 150 pods or more. Each pod contains an average of 16 seeds. In dense patches of garlic mustard, over 20,000 seeds per square foot can be produced annually.

This weed is invasive and very difficult to control once established. It tends to form dense stands that crowd out herbaceous native flora. As a result, invasion of garlic mustard into forests tends to decrease the number of native spring species. Garlic mustard can be controlled by preventing new seed production for several years until the seedbank is depleted. Various methods can be used to prevent seed formation, including cutting plants at ground level just before or during flowering, hand pulling, burning, or spot application of herbicides (optimally in early spring or fall). When hand pulling, a significant portion of the root crown must be removed or else plants can resprout. However, the best management strategy is to prevent establishment.
 


Toxicity: None known.
 

Facts and Folklore:
  • The genus name of garlic mustard (Alliaria) is partly derived from the genus name for garlic (Allium) because of garlic mustard's strong garlic-like odor.

  • Garlic mustard is also known as 'sauce-alone' because it was customary to use the plant in sauces and salads.

  • Garlic mustard is higher in vitamins A and C than many commercially available fruits and vegetables.

  • Because garlic mustard forms dense colonies on sloping land, it may help prevent soil erosion.

  • Leaves were applied externally to treat gangrene and ulcers.