Garlic Mustard - Alliaria petiola, species information page

Picture © 2001,
FBCP

Garlic Mustard - Alliaria petiola
A member of the Brassicaceae family, Also Known as -
Hedge Garlic, Jack-by-the-hedge, Poor man's mustard, Garlic Wort

A biennial plant, seedlings emerge February to March forming a basal rosette (sometimes confused with many other plants) which generate flower stalks in their second year dying off after setting seed. Basal leaves (2 - 4in accross) are dark green and kidney shaped having scalloped edges. Alternate stem-leaves 3 - 8cm across (1 -3in), are sharply toothed and triangular in shape, each leaf getting smaller towards the top of the stem. The leaves produce a distinct garlic odour when crushed. Each plant usually produces a single, unbranched flower stalk in April and May, but some robust plants have been seen with up to 12 flowering stalks.

Flowering plants average 0.7-1 m in height, but tiny 5 cm tall flowering specimens have been observed. The mustard-like flowers consist of four white petals that narrow abruptly at the base with 6 (2 short and 4 long) stamens. The flowers are 6-7 mm in diameter with 3-6 mm long petals. Will set seed even if pollinators are not present. Fruits are linear, 2.5-6 cm long and 2 mm wide. The fruit is held erect on short (5 mm), stout, and widely divergent pedicels. Fruit ripen between mid-June and late September. A single plant produces 2-422 fruit (the average is 22). Since each fruit contains an average of 16 seeds, a single plant produces 194--8,000 seeds. The seeds are black, cylindrical (3 mm x 1 mm) and grooved. The seeds lay dormant for at least one year before germinating in the spring.

An invasive plant of forest areas and margins, rapidly spreading displacing native plants becoming difficult to control. The name Alliaria refers to the garlic small given off by crushed leaves, and European common names refer to it's use as a potherb. Native to Northern Western Europe to Czechoslovakia in the east and Italy in the south, growing in disturbed forest areas, hedgerows, roadsides, streams, byways and urban areas, preferring partial shade on most types of soil. An invasive plant in North America, India, Sri Lanka, New Zealand, and North Africa.

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