James Rogers, Conservation Officer 
forestry@county.haliburton.on.ca

Forestry/Tree Harvesting Bylaw Enforcement

James Rogers, Conservation Officer
forestry@county.haliburton.on.ca

Forest Pests – Garlic Mustard, Alliaria petiolata (Bieb.)

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

Garlic mustard is an aggressive biennial (2 year life cycle) plant from Europe.

Stems & Roots: Stems up to 1m (40 in.) tall, simple or little branched, smooth or with a few simple hairs.

Leaves: leaves differ from year 1 to year 2. Year 1: the leaves in rosette form (circular cluster of leaves growing from the base of the stem) 3-4 leaves per rosette, dark green and kidney shaped with scalloped margins and deep veins which make them look wrinkly. First year leaves emit a strong garlic smell when crushed. The 2nd year leaves grow alternately along the stem of the plant. They are more triangular in shape and have coarse teeth. Lower stem leaves are larger growing up to 10 cm (4 in.) wide and kidney-shaped. Upper leaves are more triangular and smaller growing from 5 – 10 cm wide and narrowing at the tip.

Flowers: Flowers only occur in the 2nd year plants, and are small and white with 4 petals (3-6 mm long and wide. Seedpods (called siliques)may be in the axils of small leaves; 2.5-6cm long, spreading, and borne on short pedicels about as thick as the pods; their beaks slender, 1-3mm (1/25-1/8 in.) long; seeds black, 3mm (1/8 in.).

The whole plant has a distinctive onion-like or garlic-like odour. Flowers from May to June.

Below are links to further information regarding the Garlic Mustard plant

http://www.omafra.gov.on.ca/english/crops/facts/ontweeds/garlic_mustard.htm
http://www.ontarioinvasiveplants.ca/files/unwantedlettersGarlicMustardFINAL.pdf
http://www.ontarioinvasiveplants.ca/index.php/managecontrol