Sandbanks Draft Veg Mgmt Plan - Ontario Parks

APPENDIX E – Invasive Species Information Sheets
Garlic Mustard
Mustard Family
Alliaria petiolata (M. Bieb.) Cavara and Grande
Brassicaceae
Common Names
In North America, Garlic Mustard is the only common named used. Common names
used for this species in England include; Hedge-garlic, Sauce-alone, Jack-by-the-Hedge,
and Poor-man’s-mustard.
Distribution
Introduced from Britain, Belgium, and The Netherlands, and is native to Europe,
commonly occurring south of 68º, and absent from the extreme south. This species also
occurs in North Africa, India, Sri Lanka, and has spread to both North America and New
Zealand.
In Ontario, Garlic Mustard is established in the St. Lawrence- Great Lakes Deciduous
Forest Region, and is most abundant in south western Ontario and in the Ottawa region.
In the last 25 years, Garlic Mustard has spread to the Canadian Shield, and is now
common in deciduous woods on the Shield.
In SEZ parks, Garlic Mustard is known to occur in Charleston, Murphy’s Point,
Sandbanks, Presqu’ile, Voyageur, Darlington and Petroglyphs.
Biology and Ecology
General Description: Garlic Mustard is a true biennial herb, and therefore completes its
life cycle in two years. In the first year, basal rosettes develop, and are recognizable by
June. The rosettes over winter and mature the following spring. Adult plants can grow to
1.9 metres in height, and the plant averages one metre at the time of flowering.
Leaves: Basal leaves are kidney-shaped with scalloped edges, and 6-10 cm in
diameter. Stem leaves are alternate, sharply toothed, triangular, and are 3-8 cm long,
becoming smaller toward the top of the stem. Petioles are pubescent and 1-5 cm long.
Both the basal and stem leaves have a strong garlic odour when crushed, but the scent
becomes weaker as the season progresses, and the scent is absent by fall.
Flowers: Flowers are 6-7 mm in diameter, and consist of 4 white petals that narrow at
the base. Six stamens are present, with two of the stamens shorter than the other four.
Fruit: Fruit capsule 2.5-6 cm long and 2mm wide. Each plant produces an average of 4-
16 capsules, with each capsule producing 10-20 seeds. The seeds are 3mm long and
1mm wide and are black and diagonally ridged. Seeds are dispersed from mid June to
September, and generally fall within a few metres of the parent plant.
Similar species: May be confused with other rosette forming species, especially Viola
spp. (violets). The strong odour can help distinguish Garlic Mustard from other species.
The garlic odour is strongest in spring.
Habitat: Garlic Mustard can be found in open forests, and edge habitats, as well as
under isolated conifer trees. Garlic Mustard can also grow in full sun and full shade, but
grows best in semi-shaded areas. As a disturbance adapted plant, Garlic Mustard is
most commonly found in areas of repeated disturbance, and will stabilize when the
Sandbanks Vegetation Management Plan A-9
Ontario Parks, SE Zone
2009