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Invasive Species |
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Tree Killers
Garlic Mustard or Hedge Garlic
(Alliaria petiolata or A. officinalis)
 Photo 1: Dan Tenaglia (www.missouriplants.com) Biology
- flowering plant that produces a low rosette of coarsely-toothed leaves in its first year
- rosette leaves remain green over winter
- early the next spring the plant develops a tall stem (up to one metre or 3 ft) with terminal clusters of white flowers that mature into many long thin seed pods
- plant dies after seeds mature
- vigorous plants produce thousands of seeds
- seeds remain viable in the soil for six years or more but most germinate in the second year
- seeds are spread by people and animals
- no known natural predators in North America
- not eaten by deer which puts extra pressure on native plants
 Photo 2: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org. History in Canada
- brought to North America in the 1800's by European settlers to use as a potherb and medicinal plant
- most abundant in southern Ontario and southern Quebec with limited populations in British Columbia and New Brunswick
- first recorded in Toronto in 1879
- by 1900 had been found in Ottawa, Kingston, and Quebec City
- not reported in British Columbia until 1948 and New Brunswick until 1968
Impact on Trees
- grows mainly in deciduous forests
- dense stands suppress native tree seedlings, such as Sugar Maple, Red Maple, and White Ash
- harms mycorrhizal fungi that trees rely on for nutrients
 Photo 3: Britt Slattery, US Fish & Wildlife. Bugwood.org Control
- herbicide applied late fall or early spring on green rosettes
- hand pulling and removing plants with seeds
- mowing or clipping plants before flowering
- several years of control measures are usually needed
- biological control insects are being studied
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