Tree Killers: Garlic Mustard


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Name

  • Common English name: Garlic Mustard
  • Other names: Garlic Root, Hedge Garlic, Sauce-alone, Jack-in-the-bush, Penny Hedge, Poor Man’s Mustard
  • Latin (scientific) name: Alliaria petiolata or A. officinalis

Threat type

150x150 plants

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

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

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

What can be done to control this tree killer?

  • 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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